setMatrix() in CompressedMultigridTransfer and in DenseMultigridTransfer

The CompressedMultigridTransfer has methods setMatrix(...) to manually specify the matrix representing the transfer operator. The DenseMultigridTransfer, however, has not. I would like to have it as well for the latter, are there any arguments against it?

On a related note, in the existing one for the CompressedMultigridTransfer, we pass a shared_ptr by reference. To the best of my knowledge, this prevents the semantics intended by a shared_ptr, doesn't it? So if I'm not mistaken, I'd like to make this a copy.