I see your point, and it's indeed valid : I do remember a tesla crash where the autopilot simply followed an old line on the road instead of the regular one, thinking all was fine until it hit a column, killing the passenger.

But in this specific case of snow, I think this could be handled in a decent way by AI, as I would not expect snow conditions to be too hard to detect. Even something like "grip is not good enough for autopilot/snow detected on/around the road, stop on the side or slow down to the point of being impossible to have a fatal car crash until driver takes over" would be good enough.