Actually, there have been debates and a few cases, but it is only now that Patreon has clamped down so brutally, almost "witch hunting" style.
Even still this year, there were games on Patreon which did have some incest if one applied a patch, and there was at least some ambiguity about the patch source, so, it may
not have been a third party making it.
Now Zorlun indicated Patreon told him that if he creates a patch, or a version of the game on any other platform, that contains the bestiality and/or incest, he will be banned from Patreon.
That is going a completely different level, it is going from "on our platform, we don't want it or mention of it", or "our platform, our rules", which is what you are referring to and can be considered more fair and legitimate, almost to "the Internet, our rules".
Effectively, even when referring to "rules", there should be no misunderstanding, it is not a legal thing.
Otherwise, Zorlun would not have been told that even making Marc Anthony's son with another woman, thus eliminating the blood link with Myriam (which effectively, eliminates the incest, according to most legal definitions), was not enough, and all the sexual interactions between Myriam and Marc had to disappear.
To be seen if through the patch, in future, it will be possible to get still content with Marc, or not, that depends also on how complex it is to do the patching in question - at the moment, the information was that patch or no patch, any sexual content with Myriam and Marc is dead.