I'm going over to my dads later today, I'll ask for you. All I know is that when you try to turn them, the whole bolt turns on a washer that is located inside of the liftgate shell. Meaning, to remove the washer ring, and get the bolt off, you would somehow need to get your hand inside the bare shell of the liftgate.
My dad said this is a very special type used only on parts that the manufacturer does NOT want to be removed in any circumstance. Which is dumb for a simple part like that. But, I will get you an up-close shot of those bolts on his liftgate assembly.