What I don't understand is why the creator can't just upload the full cest game to his website, and leave the non-cest version to Patreon. Or perhaps I'm just a simple who doesn't know how this works.
Same reason that the incest patch is fan-made rather than dev-supported. Patreon management aren't idiots, and they're not going to continue to sanction the development of a game that has a free version off-site that openly breaks the rules. Mr Dots got around this by moving all the Dating My Daughter material to SubscribeStar and locking it behind the paywall there, leaving only his non-incest games to remain on Patreon. Patreon probably isn't thrilled about it, but it gives them enough cover if shit goes south.
Remember, Patreon isn't doing this because they have some moral objection to incest, they're doing it because the payment processors are putting the screws to them. Nobody wants to be publicly outed or even implicated for financing something potentially illegal. You have only to look at the world of shit that
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else in the past few years.