Not really true at all
There would be nothing to prevent you running a Wayland session remotely. Your remote client would capture mouse / keyboard events and send them over the network to the server. In return it would send back graphics instructions representing the desktop and your remote session would render them. The pipe could be anything, e.g. ssh tunneling.
Fundamentally it wouldn't be far removed from how VNC or NX work right now, except it wouldn't require screen scraping or conflating / discarding X primitives into a more efficient format to do. It would offer choices of how the rendering was achieved - one could imagine a really dumb client would barely any rendering and would receive bitmaps, while a rich client with OpenGL / DirectX would do everything remotely.
That aside, there is nothing to stop someone running X11 over Wayland, just like it happens on OS X, Windows.