I had quite a long chat with Richard the other day. His argument is that the tube being glued to the tyre means that the two act as a single layer and sealant will work as with tubeless (but you need less, he says). But you can fit the prepared tyre to any rim without having to worry about tubeless preparation or compatibility. The tub cement he uses allows the tube to be removed from a worn-out tyre and reused. Apparently there is a patent dating from the 90s.