I think your percentage split example is relevant and might lead to a rational analysis, certainly in terms of sexual orientation which, for want of a better word, is more of a spectrum than a binary choice. Some people are attracted only to men, some only to women, some to both, some to neither, and even if someone is attracted only to women, they can be attracted to a certain type of woman, but not another type... and there are probably as many shades and nuances of sexual attraction as there are people in the world. But humans have a tendency (and often a need) to classify things. Not long ago, there was only one "legitimate" type of sexual attraction, which was heterosexuality... everything else was denied. Since then homosexuality has become more accepted, and bisexuality etc., but it is probably a mistake to try to define everything, there will always be new categories and nuances, it is enough, perhaps, to accept that they exist and are (for the most part) perfectly acceptable in society. Labels are necessary only insofar as there is discrimination against that specific subset.

If gender is an abstract feeling of who you are, distinct from the biological male/female split, then it's fine to describe your gender as whatever you see fit, but it is silly to expect everyone to learn every term in an ever-growing lexicon, it is enough to work towards ensuring that there is no discrimination, irrespective of personal label.