But why not just do it on device?
The CPU in Vision Pro is more than powerful enough for most tasks; It's the exact same CPU that Apple are shipping in many of their laptops.
With the continuity workflow, I'll always need bring both my headset and my laptop with me if I might want to do anything beyond what the headset can do by itself. I'm also concerned about the additional latency that continuity will probably introduce.
Yes, continuity is a useful feature for when I'm doing stuff that does actually need the extra processing power of a proper workstation, but it shouldn't be the only solution.
(The cynical part of me is pretty sure it know the answer. Apple wants a locked down ecosystem just like they have on the ipad and iphone)