This is just three big corporations fighting over their respective slices of the pie, if you think any of this is being said or done for your benefit I’m sure Epic has a plentiful supply of really tasty Koolaid for you. But no pie, sorry.
I never thought about it like this. It could be viewed differently because the Xbox is a game console and the iphone is a general handheld computer, but perhaps it should be illegal to restrict users installing software on your device by any means they choose, though there's no reason for you to support those means.
But what I think you mean to propose is a restriction at the software level, not hardware level. That anyone who sells an operating system must allow any app to be installed within that OS. I think we leave it as an exercise for the reader to define "operating system" when it comes to our increasingly "smart" homes and cars.
The iPhone boot ROM will only launch operating systems cryptographically signed by Apple:
https://support.apple.com/guide/security/hardware-security-o...