Not true. The very fact that you can actually run X11 on top of Wayland is enough counter-proof. In Wayland the client is responsible for rendering, but the logic governing that rendering could be wherever you want: in the same process or in a server on the other side of the World.
To put things in perspective, that's a conceptual graphic stack.
Here "logic" is your program code. "Drawing" is the X11 and toolkit level. "Window" is a fully painted window, maybe including decorations. "Desktop" is the full desktop of overlapped windows, and display is the actual framebuffer and screen.
network between (2) and (3) is the X11 model. The drawing code is in the server, but the window is in the client.
network between (3) and (4) is seamlessRDP. The Window is in the server, but the full desktop is not.
network between (4) and (5) is the VNC model. Everything is in the server, the client is just a remote screen.
Wayland starts at 3. It takes fully painted windows, composites them and takes them to the display. You could add network transparency _inside_ of Wayland with window buffer forwarding (seamlessRDP style). But you could also add network transparency outside of Wayland, for example VNC style using a virtual display. Or at the drawing level using a networked drawing library (X11). Or at the logic level with an HTML application. Of all those possibilities, only a seamlessRDP style protocol is not developed yet.