I think this is where many people that think autonomous driving can't work are often coming from, defensive driving.

You can teach the machine the rules and best practices for not being the cause of an accident, but reacting to chaos caused by others is a whole different thing. There's an element of instinct there, there's even situations where you look at the other driver themselves to get a read.

Reading between the lines on this article, the Waymo system seems to have issues stopping or slowing in unsafe ways that don't account for the stupidity of meat-based drivers. Even if the Waymo itself is technically correct and should be able to expect people won't just drive into it, the fact that other human drivers are still on the road is a headwind for making autonomous the safer option. At some point there has to be a flippening of sorts where there's less human drivers and that fact alone makes autonomous safer even if the tech doesn't advance (and just becomes more distributed)