It seems that Patreon is really cracking down on what content is allowed on their service for some reason. It really makes little sense other than some kind of witch hunt against people who like what is considered sexually deviant art that is said to potentially influence people to do bad things to real life people.
It's not a witch hunt, it's a money hunt. Patreon is cracking down 'cuz money. Whether to save money or make more, couldn't say. The only real question is why now? The most likely candidate is probably a legality reason (something related to why you can't stream Pornhub in certain states now and Patreon doesn't wanna spend more money doing age verification), or financial (payment processors refusing service, the same excuse OnlyFans tried to use a few years ago). Patreon shareholders couldn't care less about what they are "producing" so long as it's adequately profitable...
Edit: Based on reading this post:
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It's probably more the financial reason of increased requirements by payment processors than further age verification requirements. However, the two aren't mutually exclusive.
Also, some of the explanations/examples are kinda nonsensical. Take the bestiality examples. So mythical dragon and dinosaur sex with humans is OK (Jurassex Park game anyone?), but not komodo dragon sex. Or incest. Inter-family incest, big no-no unless it's not the really point of the story, maybe? The example is Game on Thrones, where not only does incest exists, but is kinda frequent. But that's OK, since it doesn't look modern, I guess. Like seriously, how does Patreon measure gratuitousness?