You can also rely on the fact that the user is almost certainly looking directly at the screen every time they navigate the UX with the remote.
I could be wrong though, it might be doing something subtle. But even if it were, it would still be fine to fall back to a default distance of 2m or something.
Specifically, one more example, people need to use their AirPods with a TV because the rest of the household needs quiet. However, there are typically speakers already set up "correctly" oriented (especially with surround sound).
The AppleTV and AirPods could automatically communicate through the individual speakers (at frequencies we can't hear), to correlate the user's location/orientation in relation with the "optimal sitting spot, based on audio".
The location of the screen could be learned with some "Apple Magic," i.e. an AR setup process using an iPhone