I mean, does that matter exactly?
(this is more of a general reply to all your posts before this one)
It does actually, because trademark usage/infringement is entirely based around if most people consuming the media would genuinely be confused or not and is thus largely based around similar genres of media so how something is used in a purely gaming sense is really the end all be all here. An easy example is something like the video game Prey, which is trademarked (even though it's a common word), because there's a big difference between Prey (the term), Prey (the video game), Prey (the 2022 film), etc, and going off of context no one would really be confused, but another video game with a name like Prey coming out at around the same time WOULD cause an issue (and did! Prey for the Gods changed its name to Praey for the Gods avoid said potential issue in court)
The thing about metroidvania is, much like roguelike and roguelite which are also genre names built off of another game's name (albeit metroidvania is 2 different games names, but could still easily be used as examples of other genres similar like this in court), it implicitly isn't confusing to anyone who actively pays attention to video games that a metroidvania isn't
necessarily a Metroid game nor a Castlevania game but purely used as a descriptor that the genre is
similar to them, so using Metroidvania in that way isn't infringing on anything because if someone describes their game as a Metroidvania practically no one is going to think the game is literally Metroid or literally Castlevania.
There might have been a case for it if either party went after someone using the term like, immediately, but it's become so ubiquitous at this point after years upon years of usage (it's been a thing since what, the early 2000s?) that there's basically no standing against it.
