Do we think that Apple will be arrogant enough to put in actual software blocks/locks that will make it unable to be used as a PCVR headset?
It doesn't have any cabled input (or output), and most likely can't communicate and spatial data BACK to the computer - I'm happy be corrected here, but from what I've seen, the Mac "connectivity" is literally just a VNC screen sharing session (in fact it's probably just an iPad VNC app) - ie the headset doesn't communicate any spatial, or sensory data back to the Mac.
I expect it to be more locked down than Sidecar for iPads.
Will the people with the most money, with the most powerful computers, and who want the best VR they can get, be blocked by Apple from being able to use their headset?
Yes, because Apple wants them to spend that money on Apple headsets, not powerful computers.