The firmware is not the full NAND, just a partition on it. You'd still have a user partition, a log partition, and I also think something to store bug checkpoints. The Only the firmware partition (usually called system) would be CRC checked. The others can be written to. Think about your profile. Seat/Wheel/Mirror settings. Camera calibration data. All of that persists over a firmware update. Your car also ~somehow~ learns to fold mirrors or activate sentry mode in specific locations. And Homelink. It does more locally than we think!
My address takes my car to the front of my house but my garage is in the back - technically a different street. Going around the block (residential development) to park is something that should be very specific about my car and use a very limited map plot to achieve. In my mind, it makes sense to be strictly local.
Also thanks for taking my suggestion of
don't quote me on that literally