Is reading body language paranormal? If so, then every cold-reading artist in the world is paranormal.
No, Abdul, some people simply give clues about themselves in a number of ways, even by the way they look at you. If you are very attuned to these clues, you can recognize them.
To truly test gaydar for paranormal qualities, you would have to identify a number of gay and straight people behind screens so that they have no interaction, visual or aural. To make it truly correct, you might need to limit olfactory contact, because you might recognize your favorite cologne.
Of course, not all gay men give off the signals, just as some straight men will set off gaydar. I'm very straight (but not narrow) and because I live in a big city and have a lot of musician and artist friends, I tend to interact with a lot of gay people. Perhaps it is because I am not uncomfortable around gays, but I have been propositioned more times than I can count. I even had a gay stalker once. The guy was certain that I was gay and just in denial. (Apparently he never saw the condition of my dad's Playboy magazines that he hid in his third drawer, under the socks.) It seems gaydar can be fooled.