I expect you meant to say "can't dent with a sledgehammer"...While funny I have to imagine that the design of the Cybertruck crumble zone must have been a real challenge.
I mean, the vehicle's is supported by its outer shell of 3mm steel that you can even dent with a sledge hammer, so driving that into something even heavier at high speed and surviving like one will in a Model S/3/X, cannot have been an easy task to solve.
So I expect the crash tests to gain a lot of attention.
But I get your point, kind of hard to make a crumple zone from steel used on rockets and an integral part of the chassis itself.