I think the context is that foveated rendering ties sensor input (measuring gaze direction) to the rendering pipeline in a way that requires very low latency. Past a certain point reducing latency requires optimizations that break normal abstractions made by user land, so you end up with something more custom. I'm not sure why that would require a whole new OS, the obvious path would be to put the latency-sensitive code onto dedicated hardware and leave the rest managed by Linux. If a bunch of smart people thought XROS was a good idea there's probably something there though, even if it didn't pan out.