Citation needed, certainly for the case at hand, where you’re suddenly required to drive a car in an emergency situation.
(Edited to add the claim I responded to, because it looks like a few replies didn’t look at that context)
Human error/poor decisions, mechanical/electronic failures, acts of god could all reasonably be labelled as reasons.
Regardless of time.
10 seconds before impending collision, and it's hard to imagine the case where there's no time to react in some way that avoids the accident.
Remember, people fall asleep while driving cars pretty regularly. I know people who have fallen asleep driving on the freeway, woken up in the median, and just guided the car back on the road to continue.
Are they stupid for not taking breaks, etc? Yeah. But is it unreasonable to think 10s for taking over control from sleep is doable? No, it’s doable for people with the right mental state. The most common mistake is overcorrection on waking up.
In level two, it's not about "handing back control" -- the driver is assumed to be in control at all times, with the car assisting. If the car assists too much then people will start treating it as if it were an L3 system, but it's really not.