The content tags are increasingly becoming a thing but are mostly handled on a per game level. So if Space Marine has dismemberment, there would theoretically be “dismemberment” listed in the content warning list for a stream that has set their game to Space Marine. I assume this is just pulled from the ESRB/european version database, but not sure. “Mature” game means it doesn’t show up on the front page and you get a warning when you click in.
What this is rolling back was a similar approach being taken for nudity. Streamers would tag that they may have sexualized content or nudity on screen and it takes them off the front page and provides similar warnings.
So what happened was a bunch of assholes decided to go batshit insane to “protest” this and get it rolled back. Which means, funny enough, the hot tub streams and the like are once again front page eligible.