They haven't said it explicitly. But the reason that Waymo can add five cities this year is very likely they are at least at break even on opex. They likely reached that point sometime last year and it seems to have held up.

So I wouldn't call robotaxi service unproven. But I would call the idea that you can claim to be running a robo taxi service without depots, cleaners, CSRs, and remote monitoring that can handle difficult situations in a more sophisticated way than each car having a human monitor it, naïve.