SubscribeStar uses the same payment processor backend and doesn't have those rules. It's a pathetic lie by Patreon's owners who threw whatever justification came to their mind out there when they decided it was time to begin being the Morality Police and deleting things they find distasteful.No, because most of them are funded through Patreon and Patreon (probably because its funders) has a rule against incest, be it real or fictional. But they only pay attention when something gets big enough or when something gets reported.
Adding a "trigger" wouldn't change anything as the content is still there and accessible in game.
Patreon's inspectors usually come back with "Remove it or use a different platform".