>What's the problem here? Are you roaming all the time and that imposes a unreasonable cost on you? You want to stay totally off the grid and using VPN/tor isn't enough?

It depends on a remote endpoint that can go down at any point, and depends on the company's policies present and future. It is functionally asking for permission to another party to unlock it, and that would not fall under the umbrella of ownership through being able to install "my own OS" on it, at least for me. And a simple OTA update is all it takes to add multiple verification steps to it, such as providing your ID/using your verified Google account, or just take it out.

Practically speaking none of what you brought up are actually issues because once the phone connects to the internet once, it's unlocked forever, including after relocks/flashing. It's like saying you don't "own" the stuff you bought on bandcamp, because there's a split second between when you bought the song and when you could download it, therefore "It depends on a remote endpoint that can go down at any point, and depends on the company's policies present and future" and "It is functionally asking for permission to another party".