Wow, this is a pretty big game changer and not something to lightly dismiss. If the car was truly accelerating and not just coasting with no regen then there is a software or hardware glitch. Remember the throttle is fly-by-wire as is everything else. The other day my cruise control worked in the morning, not in the evening.
The next day it was working again. I called my dealer and had them make a note in my file in case it turns up again. The Service guy said this is first time he heard of this. Makes me wonder with the whole car being a giant computer how many "this is the first time I hear about this" we are going to hear about. If it was me I would call up the food chain until someone really listens. I'm sure GM would love to avoid a class action lawsuit with a few lines of code.