I think this is either an attempt to extort some money from Toyota, or he was speeding and had to come up with an excuse. The Prius is one of the few cars on the road with a full brake throttle override -- push the brakes and the throttle will automatically cut.
Here are some YouTube videos showing three ways to stop a runaway Prius:
Shift to neutral to override the throttle.
Hold power button down for 3 seconds, to shut off the car (or shift into neutral and then click it):
Use the brakes, and the throttle is overridden:
A 2008 Prius like he has will immediately reduce the throttle to zero if you do any of these actions. So this requires a cascade of multiple failures, or a scam, or speeding excuse.
And since he took it into the dealer and found out the recall didn't apply to his car, I think it is a scam to try to force Toyota to settle out of court.