The logic seems to be highlighted in these posts that
@Kuri Rinji screenshotted:
Basically SAG-AFTRA has rules about "influencers" featuring movies from struck studios in their content, so it makes sense (to this Twitter person anyway) that similar rules would apply for games from struck video game studios.
It's not clear to me if the influencers themselves are SAG-AFTRA members, though. If not it's basically non-union members voluntarily adhering to directives of a union they don't belong to. They can do that if it makes them feel good I guess but I'll keep playing what I please.