Sexual orientation does part of the job, but we can be clearer than that. There's a lot of situations it can be confusing, and those are: when it's on any character who isn't a straightforward male or female. Various persuasions of transgender, creatures that don't have a gender or sex at all, and herms and newhalves can find "gay" or "straight" being ambiguous. (Many people on F-List in particular started developing some idea that a gay female-herm is only into other female-herms, as opposed to females, female-herms, and shemales - by their gender/sex terminology.)
It's no particular coincidence F-List's gender kinks tended to be more reliable than anything else, so I think that's what was being recreated here.
Only, F-List's gender kinks might be a bit clearer, because they just have you say what you're into. Going beyond their limited scope of options, that'd be: Males, Females, Female Herms, Male Herms, Female Newhalves, Male Newhalves, Agender.
Only, there's some nuance lost there. Since all that terminology around newhalves, transgender, and so on comes from real life, where women aren't born with dicks and men aren't born with vaginas, those terms tend to imply change, which isn't a good match for the literature sexual fantasy world which contains those people born that way to begin with. I'm not sure what to do about that bit.
(Newhalves might be better known as "shemale" or "cuntboy", 'cept I'm avoiding those because they come from the porn industry and aren't very welcomed by the individuals they apply to. I think we've got an official stance of just flat-out not using them in site features ever.)