Can you name some specific examples from the video? I think it's pretty harsh to say that both of these players don't have a proper grasp on the mechanics of the game given their experience and skill level.
I haven't had a chance to go through everyone yet, but a good example is Christie. They mention she isn't top tier anymore because she lost her reset grab and her 6P string isn't as effective because you can just step it every time. While I agree that Christie is not top tier, I don't think it's for those reasons at all.
If you just mash out Christie's 6P string, sure, step all day. But Christie has to be at a decent disadvantage for that to work against a smart player. I tested this out the other day, but I don't recall the exact numbers. I want to say -5 is the magic number, but I'd have to double check. If Christie is -5 or better, she can 6P, free cancel and block your sidestep attack. In a lot of situations where you would step against Christie, she'll be at -5 or better, but they make is seem as though you can just step all day as soon as you see 6P. That's not something a high level player should be doing, and a tier list only matters at the highest level of play.
Another issue is that they do not mention her tracking options at all (other than H+K). Those matter way more than her 6P string because if the Christie player anticipates a step, she's not going to lead off with 6P. They put a big emphasis on 6P not tracking and Christie not having 6P grab shenanigans "like she had in DOA5" and that is not how you need to look at Christie in DOA6.
DOA6 focuses heavily on step and stopping step, but there was no mention of what tools Christie has to stop step. Only what she can no longer use from DOA5. Her 4P and 7P strings, 66P and throw options off of her strings were not mentioned at all. They didn't even mention the fact that her Break Blow tracks (the only one in the game as far as I know). They only mentioned H+K for tracking options, which is one of her worst options to stop step.
They also mentioned having three Christie players in FR top 8 and none of them playing Christie. I didn't see anyone actually using the new DOA6 mechanics with any kind of consistency, so I wouldn't expect them to use Christie when she can't be played the same way she was in DOA5. Citing that as a reason to justify her tier placement doesn't make sense.