The ride is most likely being monitored remotely. I changed my destination back to the start location after traveling about 20 minutes and an attendant's voice came over the speaker and asked if everything was alright. I said it was fine, but was interested that they had a live team monitoring and able to step in for customer service like that.
I did have to wait 17 minutes for the Waymo to actually show up. This success was after 3 or 4 failed attempts to request a car, so if I actually lived in the area I would probably not even open the app to check the ETA. This point is largely moot, as it's pretty clear that strategically AZ is a testing ground rather than something Waymo expects to make any money doing.
I can't wait for the autonomous future. Best of luck to all the entrants in the competition. I just hope you are able to turn a profit before investor money dries up. We've been waiting on promises of this elusive future for nearly a decade now ( ͡° ͜ʖ ͡°)