It is a new operating system with a different api and security model. Binaries on one operating system with the same processor does not necessarily run if you run it on another operating system using the same hardware.

Interesting, VisionOS. Strange choice when they could've just wrapped the "windows" in iOS and leave the rendering to the device.

Probably what they do and it's most likely more marketing than a really new OS with breaking changes to how apps run, but I haven't looked into it.