I don’t think it is necessary to lock characters to a specific preference. I don’t see how that would objectively improve the writing. Having characters with a specific preference does allow you to tell specific stories about how that affected their backstory, but that doesn’t need to be part of the story in the first place.
Due to the nature of games there is going to be a finite about of content for each companion’s dialogue and backstory. The writers can fill up that finite space with some other compelling content. The trade off for the lack of specificity is an abundance of player choice, which is preferable for me. Why write separate stories for straight and gay relationships when they can write relationships that satisfy either type?
