[indigochill]

I've poked around casually at the WebXR docs, but the main killer feature for me with Croquet et al was portals which would display the goings-on in a linked remote server in real time (you could even embed the full remote environment inside the local environment, sort of like the 3D equivalent of an iFrame).

I guess WebXR's responsibility is the interface between XR and the web, and someone else would need to take on the synchronization task to achieve that.