What he's saying is that it's not good enough to be able to control the car 90% of the time. Either it needs to be robust enough to operate safely without human

What he's saying is that it's not good enough to be able to control the car 90% of the time. Either it needs to be robust enough to operate safely without human intervention 100% of the time or it needs to somehow enforce that the driver is alert and capable of taking over 100% of the time. We can't have an autonomous car that expects a driver to take over in a dangerous situation if that driver hasn't had to maintain control the entire time. For instance, there are youtube videos of drivers moving to the passenger seat in a Tesla with autopilot on.