Remember, the rescue guy probably had an ice axe that he was using to hack into the snow. I'm guessing it has a decently long poker thingy, and is hefty. Plus he's a strapping young man who was likely using a good deal of his arm strength to hack the snow. So it's not like he was poking the snow with his finger. I'm sure the cave was sturdy, or it would not have held together in those high winds. (Plus, even a thin layer of snow offers insulation.)
The impression I got from him was he was very surprised how little it took from him and his tool to break the cave surface. Now I gather it was the entrance and that was quite shallow, but more of the cave was deeper and better protected. But insulation that allowed James's body to become frozen solid is a real lack, given the conditions don't you think? (I'm not blaming any of the men for this.)
Have you read roamer_1's post #257? I think it makes some sense and might help explain why James was suffering from such severe problems even though calling from and found in the best cave they could construct. The broken arm...shock...possibly a trek alone from one site to the other where he was found, possibly after an accident had already taken away the other two?
Assuming the other two were coherent enough to try to do what was most survivable for their fellow, his point shows that it was more likely they were lost first because the choices they appeared to have made weren't best for their injured friend's survivability. So maybe they didn't make them as it appears, but they died in a fall before James did.
Which also ties into James's condition after that...