It's Vision OS, not MacOS. You can already install Linux on a Mac, as well as any ARM compatible OS through virtualization:
"Apple allows booting unsigned/custom kernels on Apple Silicon Macs without a jailbreak! This isn’t a hack or an omission, but an actual feature that Apple built into these devices"
What do you think would happen if you tried to install Linux or Windows on a Vision Pro? Assuming Apple was to open up the device, what would that look like?