Just did a quick search on this thread as you suggested. To be honest I don't know anything about Patreon's rules in order to be completely objective, but I believe several games that contain incest are funded on Patreon and get around the guidelines using the usual landlady/roommate names and then fixing it afterwards with an external patch.
If I'm reading the situation correctly and this is indeed true and these other incest games are not funded through a different site, then I suppose I lean towards finding the dev's reasoning for abandoning BB an excuse.
It might interest you to know, that before the BB remake was being added, Kate and her sister were already able to engage in sexual relations together... The game intro literally calls them sisters.
The issue with BB from Patreon's side was indeed the incest, which had been an issue for a long, long time by the point that the Patreon page "came under review". DS was lucky to have gotten away with it for as long as he did, but made absolutely no effort to change things pre-emptively, which iirc even his own patrons had been warning him of.
Changes that would've appeased Patreon rules/oversight would have been far easier, as all the game's dialogue (the only place that references familial relations) was contained in text files. Basic text files that Windows Notepad could open and edit.