[Potentially NSFW] Why do some physical attributes seem to correlate with orientation?

I know I’m going to need to reference some stereotypes here and it’s verging on offensive so I just want to clarify that I am asking out of pure curiosity and have absolutely no disdain for gay people.

Sometimes you just “know” that somebody is gay by observing them. It’s not always accurate, of course, but sometimes gay men have a certain distinctive vocal tone, for instance. Is this an erroneous observation? If this is true, doesn’t it seem like strong evidence that being gay is genetic and not a learned behavior?