Non-consent roleplay in fiction is not permitted by their rules. We're talking roleplay done by fictives characters but that is somehow offensive to the point of being censured. I can write the story of a killer that use a lawnmower on kids in a nursery but hypnofetish fiction is too much.
The majority of non-consent in the games we are talking about is also not "roleplay". It's just fictional non-consent. Run of the mill porn sites will no longer produce results when searching for words like "hypno", "hypnosis", or "mind control". The pornography industry started taking a hardline against non-consent porn awhile ago, I'm not sure why this continues to be a surprise to people.
As far back as 2021 Patreon had a clause in the 18+ category of their guidelines that stated "fetish creations that are hard to distinguish from non-consensual sex" are not allowed. That statement has always included hypnosis/mind control, the only difference now is that they specifically call them out. Which begs the question, why haven't they been banning for it up until now? Most likely because they make a non-insignificant portion of revenue from it. It's very much don't ask don't tell, which is why the bans have not started rolling in en masse. Patreon is not constantly patrolling creators' pages and are really only making moves against creators in blatant, egregious violation. Since the guideline update, we have even seen a few games that were under review be given the OK by Patreon, even though the content of the games are still definitely in violation of the guidelines, the creator's page and social media are just now considered "clean". The changes are still and have always been just for optics. All that's changed is toeing the line got a little bit harder.
Regarding your comparison to ultraviolent content still being allowed as long as it's fictional, not much I can offer besides: that's just the way it is, at least in America (which Patreon is an American company). Basically any kind of violence is okay, but a lot of legislators would kill to ban ALL forms of pornography, not just non-consent. See: Texas.