mcat, i honestly don't know if you're intentionally searching for ambiguity to support some mysteriously hipster ideology, irredentially (not a word, i know, don't argue about it, you know what it means) contrarian or simply an alien life form that shares so little in common with normal humans that communication difficulties are inevitable.
some of my thought process is based in studies i've seen, papers i've read, etc. but inevitably it's chiefly based on my own personal experience. and i can not recall an instance where i've been in doubt regarding the sexual identity of a person i've been attracted to. it's possible, even probable, that i've been incorrect in my assumption of their sexual identity, but i cannot recall a single occasion where i've been in doubt at the time of attraction. like your example with the anonymous, sexless hands jacking you off. i may have led a very boring life, but that's never happened to me. if it had, i'm almost positive i'd have no more doubt about whether i'd been attracted to those hands or merely been stimulated like a prized ropinfeet bull hauled in for harvest than i have regarding the action of gravity upon an apple.
i simply don't comprehend your professed lack of comprehension..