Well you can't run your own OS on iPhone hardware without jailbreaking but that's beside the point. You don't own your Xbox not because you can't run Playstation games on it but because the manufacturer put a digital lock on it they control which denies you the ability to run software they don't approve of on it.

I think we can do better than "well you own it because you're technically allowed to attempt to break the lock." We can demand that users be given ability to remove the lock.