I think your second point is true for lots of (all?) vehicles today, which have an architecture of multiple modules communicating over a CAN (car-area network)

I think your second point is true for lots of (all?) vehicles today, which have an architecture of multiple modules communicating over a CAN (car-area network) bus. I did a firmware update on my Pacifica PHEV while I was driving it, and though I lost the ability to listen to the radio and change settings on safety and convenience features (rain-sensing wipers, blind spot detection, etc.), the car still ran fine (and all of the safety features still functioned).