^ i never say he wasn't,
he is a thinking weapon having some fun around before showing his full power and serving his own interests not the gantzers
"sleep with me tonight, sweety" ~sakura_hana~
I don't even think that's Nuri's real body. If the information Gantz provided is correct (smart characteristic), then Nuri would not be stupid enough to expose himself to Kyou and Nerd, or let a complete stranger use your head as a weapon of mass destruction.