If you imagine a scenario where this works well enough that it's a viable alternative to actually buying a Vision Pro for development ... I can forsee it being a problem for them in terms of (a) direct sales - I could easily see shops fitting out their dev team for 1/4 the cost with Quest Pros instead of Vision Pros but more importantly (b) concern that it will lead to crappy apps being developed. That is, devs using non-Apple hardware will naturally curtail what they build to things that actually work in the dev hardware they are using. That means advanced features of the real Vision Pro won't get properly supported (or omitted altogether).

Of course, that is still miles away from where this is now. But it seems tantalising that it could possibly go there.