I'm going to disagree, at least in principle. This is a porn game, but I don't think it's necessarily wrong to limit the porn options available based on what would be 'realistic' for a given person. Strong characterization is one of the bedrocks that can make an AVN so compelling, and some characters really are going to struggle with an idea like sharing a lover with someone else. Riding roughshod over that sort of objection may titillate, but it also flattens the distinction between characters. IMHO, that's too high a price to pay, at least as a general rule. As much as I'm down on the developers for the way they handled the end of the game, I'll defend their right to insist that some fantasies are beyond the scope of a given game.
HOWEVER...
If you want to go that route, you have to make it abundantly clear WHY those fantasies are impossible. We're talking about something that goes against who that person is at their core; you can't just live in narrow edge cases where asking for the impossible would
work if you use the right wording. You need to make a clear, compelling case for why a character couldn't go along with something, and the case needs to appeal to a broad swath of players over a very wide set of circumstances. Try to get too cute with it and it's going to feel like an unreasonably convoluted secret path, or worse, like a bait and switch.
And that's where I think the devs screwed up here. I can easily buy that Jaye is just too possessive to share 'her' MC. I cannot buy she'd suddenly reverse course on that because the MC made a point of sulking about a girl he had to give up for Jaye; if that trick worked, Jaye/Tara would be an easy thing. Nor do I buy that an MC who DID decide to cut things off with Mallory to focus on Jaye would suddenly want to start things back up with Mallory at the 11th hour. He abandoned Mal (sexually) weeks ago, so he's clearly comfortable with that idea at a basic level. What makes him think things would work smoothly if he hits Ctrl-Z now? Why risk something - something that was so precious he gave up on Mallory for it in the first place - on such a longshot? And why would Jaye take the MC's acquiescence as a sign of his love for her rather than buyer's remorse?
The answer, obviously, is that they wouldn't - if this weren't a porn game. Maybe you could make this twist work if you spent several chapter setting it up and seeing the characters struggle with the changes. Maybe. But trying to cram it into a single scene in the chapter that had lots of other loose ends to tie up? No way. It not only feels fake, it damages the integrity of the characters involved. It's the worst of both worlds: the characters are flattened into bland tropes, but we still don't get the extra titillation that should go along with that. Everyone loses.
Plus, it really grinds my gears the way the game promises us that we should "play our conscience" in the intro, then slams us with a folding chair at the end for daring to think that the proper way to start a polyamorous relationship is with a heaping helping of honesty. Evidently our 'conscience' should be a finely tuned propensity for gaslighting and deception. Fake it 'til you make it, MC!