That was kind of rare for these types of games. Really rare. But they wanted the best career payoff "Superstar" to have some gates.
Sure, but here's the difference in how Melody versus, say, Depraved Awakening accomplished the same thing.
In the former, there's a content gate that you can't possibly
know about until it's too late. Yes, you can
assume (and you'd be correct), but while the game nudges you away from Amy (your doubt over whether or not it's a good idea to bang Melody's aunt), Rebecca (Melody asks about the cat that wanders around as if it knows the place), and Isabella (a reminder that she'll continue to live an itinerant lifestyle), it does nothing of the sort with Sophia and/or Xianne, much less their possible interactions with Melody/Melody and the MC. With the other NPCs, the game tells you what you need to know. It doesn't hit you over the head with it, but it's in the text. Whereas with Sophia and/or Xianne, the text gives you every indication that Melody's really into them. In other words, it's telling you the opposite of what you need to know. That, to me, is bad writing. And it's not like they couldn't have slipped a line or two in there; the game's intolerably wordy already. Surely yet another internal narrative expressing uncertainty about Xianne's unabashed sexual aggression, or a conversation between the MC and Melody wherein they wonder if having Sophia as a bandmate
and a lover is wise — this could very easily work just before the point the MC is considering having sex with his former/current bandmate and former lover — would take care of this oversight.
In Depraved Awakening, there are also multiple outcomes and endings...but they're
paths, not gates, and they're not necessarily exclusionary. There's more than one way to get to whatever content/LI you're after; I think only the assassin requires needle-threading, and all the choices are presented as just that:
choices. None of those choices are hidden from the player, like Sophia/Xianne is in Melody.
Obviously, the game's long over and none of this matters; nothing's going to change at this point. But even more sophisticated games like Deliverance occasionally make this mistake: being explicit (even if it's subtle) about the consequences of your choices, but then gating content due to a choice you couldn't possibly predict would wall off that content. I don't mind if someone wants to make all the gates impenetrable to the player (though it's certainly not my preference), but making all but one of them explicit is clumsy, and specifically telling the player that a choice is welcomed by the primary love interest, only to cut the player off at the knees as a result, is worse than clumsy.