I agree with the <5% passing, but I really like that distinction between passing and going un-noticed. Though I've gone out dressed and gone un-noticed, I don't think I pass. I had a conversation with a friend about this and we both think that it's not just the body size, frame, build, type, etc. but also the aura - by which I don't mean some spooky thing but just things like subtle mannerisms and behaviors and ways of doing things that we normally don't notice when present in a woman but do notice when lacking in what appears to be a woman (even though we may not be able to place our finger on what seems to be strange).
But I think part of it also has to do with the setting and context, and the culture of perception. I don't know - now I'm beginning to babble...sorry!
