Why is mps_copy_ not registered to copy_stub

Hi Community, I am currently working on integrating a hardware backend and when I start with copy op register I saw the following code in aten/src/ATen/native/Copy.cpp

#ifdef USE_MPS
  if (self.device().type() == at::kMPS || src.device().type() == at::kMPS) {
    return at::native::mps::mps_copy_(self, src, non_blocking);

What I was expecting to see is something like

REGISTER_DISPATCH(copy_stub, &mps_copy_);

Is there a special case for copy op registation?