You should get able to restart the infotainment system without restarting the car. Push and hold both the power button and the >> (fast forward) simultaneously until the screen goes black... about 5 to 10 seconds or so. That reboots the system after a few seconds and hopefully clears your...
If they are like my dealer, they let the car run at idle for a while as they do other checks. They tell me it's to charge the battery and prevent battery run down while doing the PDI. I wouldn't worry too much about the mileage.
Didn't I read that the early build quality checks identified body panel fitment issues, and valve issues on the V8's? Maybe it is being checked for valve quality...