It's hard to understand why recovery of dead bodies is so hard. If people can go there and walk past them, how hard would it be to pop the bodies on the sleigh, strap a rocket and push the ignition button?
yes one of them is fake. The one with the skull is a fake or a photoshop. The bodies are perfectly preserved due to the freezing temperatures. There is no way it would be just a skull.
George Mallory's body is partially skeletonized. Decomposition in freezing temps is slow but it does happen.