It's sad to see Patreon yet again smashing nice project into pieces for nothing more than a PR move. It is something I see regularly in my line of work.
The whole goal of having those fetishes is to fill out kinks and make scenes more exotic and interesting just with the premises. A man and a woman having sex, it's nothing extraordinary. A brother and his sister, wow, that's something else. And adding it into a interactive game mean you can get involved in the story itself and make it so much more interesting than watching porn about it, where you have obviously no bearing on the scene itself.