The wing is the same aircell with the same inflator and buttons and all, but it's located around the tank on your back. Which is why if you inflate it completely, it will indeed turn you backside-up .
Oh Neptune, here we go again.
This is just plain wrong. We used to routinely inflate our wings (all kind, even me with my Xdeep stealth, and god knows the inflation volume is low on the back on that one...) until the OPV burps, no-one ever faceplanted. We could all be vertical without trouble. For what it's worth anyway, no BCD is designed to keep your head up (except I think the Masterjacket from scubapro).