Apple hasn't made it exactly clear AFAICT, but I suspect that foveated rendering might only work in the managed RealityKit environment where Apple controls the

Apple hasn't made it exactly clear AFAICT, but I suspect that foveated rendering might only work in the managed RealityKit environment where Apple controls the entire rendering pipeline, and not inside applications which implement their own rendering from the ground up using Metal, for exactly that reason. There's nothing in the documentation about foveated rendering in Metal apps, and it is something that engines would have to be explicitly aware of if they do any kind of off-screen rendering.