I think one insight (that's maybe not obvious enough on their landing page?) is that their product appears to be multiplayer out of the box (in the same sense that Figma is) which I think you'd agree is a pretty significant value add over your proposal of Unity + Meta simulator.

This tool is aimed at Interaction, Spatial and UX designers and provides a no-code way to very quickly go from idea to device. No technical setup needed.

The core goal is to have a much faster and more affordable iteration loop than the current ways of doing AR and MR prototyping. Which we hope produces far better products going forward!