Why're you so willing to forgive the sins of past battlefield games in this regard, as their portrayals of war featured many elements that regardless of you specifically think, to any historian, is laughably out of place? There's genuinely no difference, (there are many accounts of soldiers using weapons that weren't standard in their specific army for instance, that's a thing that happened, so it's fair game).
There's a big difference. They're on two entirely separate levels.
The Battlefield series has always taken some artistic liberties in the way things have been portrayed. In BF1 the Sentry with the MG08 running around wouldn't have occurred in WW1. The weapon options had a large amount of prototypes. The term Panzer wasn't used during WW1. Aircraft-mounted rocket guns weren't carried around. With the games like BF4 real-life soldiers don't use any weapon they like in a pre-defined Battlefield while aimlessly running around on their own or in small groups driving or piloting whatever they want while fighting over arbitrarily placed flags. Those are all things included in the games that are unrealistic, inaccurate and ahistorical - they simply are not things that fit in with a true portrayal of their chosen setting. The difference is in how they are integrated into whatever setting the game goes for and the extent to which they fit in with a consistent theme.
Despite those issues the games still always showed their settings in a serious manner, outside of gameplay and silly things as the result of player agency. Battlefield One was still a gritty, atmosphere portrayal of a WW1-based setting, Battlefield 4 still had a noticeable underlying basis of being a Modern-day themed setting despite the plot and locations and such being fictional. The way they realized those settings and the effect the inconsistencies with realism or accuracy had on them is at a whole different level with Battlefield V from what we've seen of it so far.
In those previous games, the issues were not as noticeable on a surface level. They were not an aspect of the game that had been specifically implemented with disregard to the theming of the game and maintaining the feeling of a consistent setting. Despite being unrealistic in how they were put into the game, it all still felt like it had a place - the Sentry with MG08 didn't exist in that form, but he still felt like something from WW1, the gasmasks were entirely different fro WW1 era gasmasks but they weren't some obvious out of place design, the Char B1 tank despite not being made or used in WW1 still matched the theme and tone of the setting the game was going for. Regardless of those ahistorical inclusions in the game, it still maintained a consistent feeling of being the setting it was claiming to be, outside of the decisions like regenerating health or reviving palyers which were for the sake of it being a video game. The Battlefield games up until now have always been this way, realizing their settings in a way that come across as a believable abstract of the setting they try to be, they've all felt grounded within that theme in aesthetic and tone.
The games always made an effort to integrate those things which didn't quite fit the theme in a way that made them feel like they fit the theme. Reviving players instant makes no sense in terms of accuracy, but they still used the equipment that would have been available at the time. Repair tools don't magically fix vehicles, but they still looked like their real-world counterpart and made sense with the theme. Ammo or medical boxes don't cause those things to spontaneously appear, but they still matched something you'd expect from the time period. BF3 or BF4 or BC2 had planes and helicopters that didn't behave in the slightest like real versions would, but they still looked, sounded and had equipment that would make sense. The unforms would be similar to those worn at the time. The camouflage or vehicle colours aren't outlandish and brightly coloured. The weapons that are chosen to be in the game are from the time period and have relevance to the setting. The Battlefield series has always made a big attempt to make sure that even when things that don't accuracy fit a setting are included, they are still authentic feeling to that setting. Those things didn't always make sense, but they weren't shoved into the game with disregard for keeping a consistent, cohesive theme. Any historical liberties taken were integrated into the theme in a way that was at the very least an attempt to make them fit and had a justification for not being entirely correct.
That isn't the case with the BFV trailer. Those in-authentic elements are now front-and-centre. They're no longer integrated into the theme in a way that feels like they complement and are something that adds to the overall feeling, it's the oppisite - they now detract from the feeling of having that WW2 theme. By all means give players customization options, but it should still be done in a way that doesn't take away from realizing that setting. Give a Soldier playing on a map set in the Pacific a Katana or one in Normandy a more fitting type of sword, give a pilot character a flight jacket or have characters in Africa shirtless or in tank tops, or let players choose a variety of different camoflage, smocks, pouches etc. By all means do that sort of thing in the game, but do some in a way that still fits the setting and theming and is not out of place in the context given. Don't just give a katana to a British commando in Normandy for some reason. Don't just have a character with a biker jacket show up. Don't just shove these things into somewhere that it knowingly does not fit the theme to the extent that it'll feel extremely out of place even if it is something from the time period. Again, put the effort into making it feel like it fits, rather than having been thrown ontop with disregard for keeping a consistent feel, do it in a meaningful, nuanced way rather than something that's so apparent as being against the settings cohesion.
It's a bigger problem than those inconsistencies in previous games because of how it very clearly is jarring in the context the game is going for and how there has been little or no attempt to adhere to the theme with their inclusion. Rather than the usual approach of taking something that might not quite fit but then making it still feel like it fits with the rest of the games setting, this time it's done in a way that dillutes the overall consistency and claims of being the setting it tries to portray. It's simply down to the amount of these things being done in this way making the theme of the game feel like it isn't there, like it's gone from "This is a WW2-themed game" with a certain level of abstraction to portray the setting at, to just a mix of all sorts of different things from the time without context or even an attempt at fitting them into the overall theme - it's just "This existed? It must fit then!".
As said many times, these things fit the broad context of WW2. The Prosthetic exists, the Katana was used in WW2, there were jackets like that - but the fact that they existed in itself does not mean they have been integrated into the games chosen setting in a way that doesn't detract from it. The historical liberties and inconsistencies regarding the customization system are this time without the gameplay reasons for being like that, without the player agency that results in things like standing ontop of vehicles as they move and without the attempt to at least make it feels like it fits the context they're shown in.
The games have never been realistic, accurate or an entirely perfect portrayal of their chosen setting, but they have shown their setting in a way that at least wanted to try to represent it in a way that looked and felt serious. The tone and atmosphere of them and what was included in them for the most part still matched what it was trying to be.
That isn't the case with the trailer. It overall lacks a cohesive representation of the setting, that's why it's different - it goes well beyond the typical way the out-of-place things are done, to the point the setting doesn't quite feel like it's taken seriously.