What if the car "works" under all conditions, but moves extremely slowly, takes huge detours to avoid tricky roads etc. In fact what is stopping this "technically correct" approach: car calls a human driven tow truck, gets hitched and towed to destination?
Decency and reasonableness. Neither John nor Jeff are going to try to lawyer they way out of losing.
If the car moves extremely slowly in a major city, it would get banned after a handful of traffic jams, and so wouldn't be commercially available. And anyways no company would risk the bad PR of launching a car that tops out at below the speed limit.
If the car calls itself a tow truck, it has obviously failed to drive itself.
If the car is programmed to avoid tricky roads, it can't "drive everywhere in all conditions" per SAE.