Yeah, I know running X11 over the wire doesn't hold up, but that's not what's being done here with Wayland either; since we're locally grabbing pixels off the virtual display and then flinging them over the wire via custom UDP protocol, X11 vs pipewire only matters for the initial handover.
The compositor may be able to transfer image data to PipeWire in zero-copy fashion, which may then be consumed by hardware video encoder without any copy on the path. I'm not sure whether you'd be able to do that using Xorg as display server.
