Airpods are not demonstrably better than other headphones on the market by any other standard than their integration with iOS, that sounds like lock in to me... "Oh you've got an iphone? If you want the headphones that work best with iphone you better buy them from the company that makes iphone!"
This kind of feeds in to the original point though. The iPhone supports the full bluetooth feature set so 3rd party headphones work fine. The AirPods are only able to do a little bit extra by having the ability to have any part of the OS changed to support them better. This is something that requires a high trust level, you could never expose this access to any 3rd party device.
So it put the AirPods on a level playing field with everyone else, we would have to cripple them because they would have to exist in the same low trust environment. Is this actually better for consumers?
It depends on the size of the company doing it - i.e. on how impactful the lock-in actually is. But I feel that certainly a boundary past which not crippling such proprietary integration would be more economically harmful overall, despite the convenience.
Correct. "It just works" means either they're accessing a private API or there's unique parts of the firmware that no one other than Apple has access to.