Miles driven is only one axis of many, does Waymo get from A to B as quickly as the average human driver would, or does it play it safe by staying in the slow lane and taking suboptimal routes to avoid challenging areas?
Narrow streets packed with park cars, lots of bikes and pedestrians jaywalking, a homeless population that spills over into infrastructure, etc. It’s a good test case for most US cities that aren’t NYC.
A LIDAR is pretty much all you need to avoid a collision. It's a pretty forgiving environment.