Maybe I'm old-school, but I really dislike all this fluidity in NPC sexual preferences.
Nothing against any hetero, homo, bi, something-sexual but having NPC changing who they are to the core (sexuality isn't a superficial thing) is bad for different reasons, in my opinion:

1) Makes the game less believable, since in reality people don't change their sexual preferences to accommodate you;
2) Makes the NPC less defined and, for this, less memorable (even if only by a little). Memorable characters have well-defined characteristics; if those characteristics are fluid and can change on a whim, then the whole concept of the NPC starts to blurry.

And, last but not least:
3) It's good to be rejected, sometimes, it teaches you to deal with things. I will always remember, in ME: Andromeda (probably the only memorable thing of that game) I really wanted to romance the red-haired girl NPC from your crew. I tried my best but, in the end, she revealed to me that she prefered women and was not interested in me. I rejected all the other romances options for her and I was rejected in the end. And you know what? It was amazing. Finally, a well-defined character who doesn't try to accommodate me in every way possible. I just had to accept that not everyone is going to be interested in me (my character). A good lesson from a videogame, who would have thought!
This is also the reason why I really disliked the "washing" of current NPC personalities. People just seem unable to deal with the "NPC disapproves your actions" or "NPC isn't interested in you".

I know that, in the end, we are just talking about a minor aspect of the game, but these are my two cents. In my opinion is just better to have well-defined characters that may not be interested in you, regardless of your orientation, than to have all of them just ready to accommodate your every fantasy sacrificing who they are in the process.

Maybe it's just me ¯\_(ツ)_/¯