I can only get the favorite radio stations when I am HotSpot connected to the head unit via phone. This leads me to believe the that the favorite radio settings may be associated with a specific Google Account so that different drivers can have different saved radio settings when their phone is connected.
This makes sense accept if there is no phone in the car and the driver wants to play stations that they normally listen to. Would be nice if the favorite stations were saved locally to the head unit and would only be overridden when a hotspot link is made by a newly connected phone.
That way, the elegance of the radio favorites UI can be available to the user rather than just a blank canvas. In this state, the only option to llisten to the radio is to go to the radio tuner and manually tune to local stations (that may already be tagged as favorites by the user but not known by the Head unit if a phone is not connected).
Thanks for considering my request, Dasaita!
