Absolutely, having only a single version of the script and art keeps things easier to manage. Unfortunately, it's not only that. Patreon has already proven in the past that the easiest workarounds to allow incest-related themes in games (e.g. providing a simple script to enable specific options or dialogue, allowing the player to rename the relationships) are not enough to guarantee an exemption to their rules - if it's in the script, you're out. Some authors already burnt themselves, and now nobody is willing to push the boundaries, which is understandable. For comparison, just read the ridiculous Patreon rules about consent:
Patreon is obviously going the extra mile to preserve their bottomline, and authors are caught in the crossfire; so, in turn, they do the same. It's unfair and undeserved, but when money is involved, matters of principle are the first to get silenced.