I suppose, similar to how a lesbian can't proclaim to not being straight if never having tried a cock before. In a perfect world, I guess there would be no generalizations or stereotypes, and no barriers, and people wouldn't feel the need to be labeled and caught up in entrapment of one side or the other.
Tpbm has an androgynously challenged cat who thinks it's a female and tries feeding kittens, but of course fails utterly and pathetically.