A lot of people seem to be discussing spatial audio as if it's only head tracking.I don’t think I would want the driver to be playing around with spatial audio while driving.
Then realises this feature is for the people in the back driven by the chauffeur.
I think in this context it is that spatial audio = dolby atmos = surround sound audio.
The feature here is that you will get the proper dolby atmos 7.1 channels (or whatever it is) from your upgraded sound system using Apple Music. Not that it will track the drivers head position in the car...