The spherical cow is a simplified abstraction that doesn't accurately model anything in the real world.

Phoenix, AZ, is in the real world, with real roads and real customers for a real, if limited, self-driving service. Waymo’s self-driving is far less vaporware than Tesla's.

It was meant exactly in this sense, namely that the conditions in Phoenix do not resemble the challenges in the rest of the world.

Phoenix gets about 310 days of sunshine per year, only 200mm of precipitation with no snow, no fog, ...

...shitty drivers from the other 49 states, blue-haired old ladies who haven’t seen the inside of a DMV in 20 years, and massive dust storms. That 200mm of precipitation happens over a couple of days. I’ve driven in every state in the western US, and those rain storms are scary.

And what do the Waymo vehicles do during such a dust- or rainstorm? Just carry on providing rides, or go into a safety shutdown mode? (Genuine question; I have no idea.)

> what do the Waymo vehicles do during such a dust- or rainstorm?

Do what most reasonable drivers in Phoenix do. Pull over and enjoy the view. (Phoenix dust and heavy rainstorms tend to pass in ten to thirty minutes.)

It is likely much easier to expand territory bit by bit and improving the baseline than it is to throw everything and the kitchensink at essentially unproven hardware. The first will likely work, the second will end in blood.