The article is not asserting that self-driving cars are always better than humans, but simply that in controlled conditions in SF/Phoenix, they seem to be doing a better job than humans. This is already pretty amazing.
Yes, many places are harder to drive in than SF and Phoenix, but they're harder for humans too, and Waymo & co will continue to get better as they get more training data, better sensors, and bugs get fixed.
1976 was the last time it snowed in San Francisco. I wonder if the Waymo software has logic for precipitation/temperature i.e. shut it down. I'm guessing it requires human intervention although hopefully in a timely manner.
Yes, many places are harder to drive in than SF and Phoenix, but they're harder for humans too, and Waymo & co will continue to get better as they get more training data, better sensors, and bugs get fixed.