You're talking about the MCU (media control unit), which is completely isolated from the critical driving functions of the vehicle. As its name implies, this unit mostly drives the vehicle's entertainment functions. It's actually incredibly confidence-inspiring to me to know that the MCU can go entirely offline and the vehicle continues to function at 100%. This seems like it must be table-stakes for all vehicles, but I've seen more surprising things.

I'm not sure why you mention cell coverage, given that it is entirely unrelated.