There is no good fix. It’s a Google thing. People have tried using roots and OBD2 fixes, but there is no easy solution.
I don’t know the Spotify app that well, but it should be possible to scroll through songs on a playlist using controls on the steering wheel or voice control. Those methods shouldn’t trigger the scroll warning.
Alternatively, he could skip Android Auto and use Bluetooth instead if it’s only connected for the music. That’s what I do for other music apps and the steering wheel controls also work just fine that way too as long as I have prepared a playlist in advance.
Yes Android Auto is needlessly complex. I don’t think the parking sensor is the cause anyway.
Perhaps there are some options on the phone to disable screen takeover or pop-ups or something. Deleting all app permissions is my best guess.