I mean a wireless wearable computer would have network lag but the important lag – between the rendering GPU and the screen – would be nil.
I mean streaming the video data to the headset Miracast-style would be dumb, I agree, but afaik all the rendering hardware in the new Apple headset is inside the headset.
The new Steam Deck and its copycats have proven that a compact gaming-grade PC is doable. If not fully contained in the headset, then make a little fannypack with a cable up to vr headset, but you can walk around untethered otherwise.