maybe i am missing something then, because last time i played (about 2 updates ago, i prefer to save a couple of updates up to get a bit longer playtime), neither nia or sylvia would do anything with us (outside of the main plot scenes) no matter what their mood was, and neither of them had horny scenes (yet)..
the other three (the ones that stay in the bedroom at all times) would interact in the repeatable scenes regardless of the ration setting.
btw, im not being critical, just giving you my experience with the game.. love the game, keep up the good work :)