IMHO, our criterion is "we only need to implement what apps really need", and for the moment, that app probably could live with a stub for D3DXCreateTeapot. When we run into a complaint about our lousy teapot, we can create a better one. So relax, just do a stub, and move on to more important things.
Also, as Roderick says, sucking tables out of Windows is not ok, for copyright reasons.