"I know it’s not going to cancel because it’s a robot"

I won't be at all surprised when they start calculating their profits in real-time, if they aren't already, and cancelling or delaying trips that are deemed unprofitable in the moment. They are robots after all.

Waymo already does that through its surge pricing mechanism and limited availability of cars at busy times. And if they really don't want to serve you they'd just not let you book.