"The person in the driver's seat is just there for legal reasons" -- but note just how closely that person's hands are to the wheel, in an obvious state of readiness. That person is 100% ready to take over the car if it messes up.
Tesla had the luxury of running test drives until they had a success. This is a different thing than putting a car on the road with no steering wheel and saying bon voyage. The first is a demonstration of a single successful instance (which is probably repeatable on average); the second is a much stronger demonstration of a > 99% success rate.
