I think the other way to think about it is that Waymo is probably in the 99th percentile for not being distracted and 99th percentile for reaction time, always, just from a pure sensor and computation standpoint.
From a purely technical perspective, I would expect a Waymo to react to unexpected external stimuli much, much faster than a human. It gives the Waymo options that are unavailable to a human's slower reaction time.
Do you have a solution for preventing humans from driving while under the influence of alcohol or drugs? Or even preventing humans from driving while texting?