I'm not demanding that all games in the genre I like have to follow my exact preferences to the letter, no.And aren't you doing that too by believing that all games with those rules are boring for everyone? the vast majority of us love those "clones" you mention.
Why? Name one good reason a dev can't decide to not make a character a love interest. This is what I don't get- the "I like mother/son so every game with a mother in it must make her romanceable" attitude.Not to mention, if the game is going to have incest, and the mother is going to show up, it would be ridiculous if she wasn't a possible sexual interest for the MC.
Personally I think it's bizarre to have a hostile reaction to relationships that exist before the protagonist becomes interested in the woman- to me that's the opposite of NTR. But yes, it's extra silly for people to be throwing tantrums when (according to the overview at least) the mother isn't even in the game at this point.What you have a point (the only thing) is that for now the mother is out of the game and no one guarantees that she will appear soon (or even will), so that she has a boyfriend is not relevant for now.