If you know this type of game, the real answer is pretty obvious:
All straight + incest content is only added to draw in the 90% of players with a "normal" taste to patreon. But after a couple of years, most of the content is about NTR, furry, futa, bukkake etc.
For example look at Warlock and Boobs; the MC's mother was added like a year ago, but hasn't gotten more than a blowjob in the 12 updates in between. The sister is there for like 5 years and has 2-3 scenes.
Or Seeds of Chaos, advertises with the cuck/gay content being optional, but 4 of 5 scenes in every update are not of the straight type.
Same in this game, though Regina isn't even the mother without the unofficial patch. Don't know why the game has an incest tag.
Rule of thumb: If the game has certain niche tags, like loli, futa etc. then you can assume that the devs don't put this in to do the sexual minorities a favor, but because they want to make a game about this type of content. Everything else is just bait to get the majority of payers on board.