I'm the author of this. It was certainly surprising to learn that a lot of what AVs are doing right now is limited by the amount of power available to the computers. It didn't make it into the article in full, but we were told that in general more computing power means detecting and classifying more object types, tracking those objects over longer periods of time, and doing more detailed motion prediction and planning across longer time horizons. They were explicit that the power they can squeeze out of the vehicle's alternator is currently a significant limiting factor to the performance of the system.