I wish I was surprised, but Apple TV has always been little more than a hobby for Apple. Though, it does sort of boggle the mind that Apple built a “pro” feature primarily for people to watch movies on their phone, all while leaving the TV completely unaddressed.
It’s might be related to the fact that the current Apple TV model was released two years ago. It might be missing some tech required for this to work (ie to let the earbuds know the location of the source device). Or basically lacking the computing power.
My guess is the tech might there (even if it means a new Apple TV model for the readons above). But it’s actually more complex since Apple TV never sits in the middle of the screen, but below/to the side (or even behind the viewer, with a beamer) and with big screen TV the effect simply does not work. There would need to be some sort of a calibrating process to let the buds know what is the relative position of the source of sound (ATV) to the screen (TV/beamer) so the sound can be positioned properly.