The game doesn't need the incest patch. Someone made it because they wanted to change it up.
I'd argue that this game is one of those times where adding the incest patch actually makes things worse.
Incest patches work best in games where the story has clearly been written with a "LANDLADY" and "ROOMMATE" in mind (when you get awkward lines like "We can't be together, because the world would never understand the love between two roommates!"). In those cases, the incest patch is pretty clearly just fixing the game back to what it was already supposed to be, and only wasn't because of Patreon bullshit.
But in this game Ellie being your half-sister and Rachel being your stepmom is actually part of the story dynamic, and is clearly the intended relationship between all the characters. Full incest patch just makes things make less sense/makes the story worse. The backstory works best if you just keep things the way they're supposed to be.