A PhD should be, at least in theory. Whether it is or not is a question - and "until dissertation" is doing a lot of work in that sentence. Importantly, a staf

A PhD should be, at least in theory. Whether it is or not is a question - and "until dissertation" is doing a lot of work in that sentence. Importantly, a staff scientist position will never be. If you cannot tie your project to one of my grants, you are losing me money. For a student, that might be acceptable. For a staff scientist, it's not.