To add some advice you didn’t ask for: I’d recommend to just use .pt as the extension.
As you rightly note it’s been long ago that this used to be a tar file, and pth isn’t particularly compatible with Python’s “.pth” path files (there is an open issue to standardize on .pt in the PyTorch examples).
I agree, since it doesn’t seem like we actually need to tar/untar files when we use Pytorch’s save and load_state_dict functions. Hence, it’s just unnecessary overhead to explicitly write out the tar