Tyranitar's body in fact cannot be harmed by any sort of attack. You can check in-game that now matter how many times your T-tar dissapears by CC, his graphic is always the same, without a single indication of his body being injured.Tyranitar is also described as having a body that cannot be harmed by any sort of attack, which literally never has been true or made sense. Pokédex descriptions are a non-argument.
All of this is obviously speculation and I'm not looking to argue something that nobody here can prove, but this new dragon doesn't feel like a fully-evolved monster to me for some reason. That being said, I might be biased since I really do not like its design and hope that it changes into something better upon evolution.