Have you been in a waymo? It knows when there are pedestrians around (it can often see over the top of parked cars) and it is very cautious when there are people near the road and it frequently slows down.

I have no idea what happened here but in my experience of taking waymos in SF, they are very cautious and I'd struggle to imagine them speeding through an area with lots of pedestrians milling around. The fact that it was going 17mph at the time makes me think it was already in "caution mode". Sounds like this was something of a "worst case" scenario and another meter or 2 and it would have stopped in time.

I think with humans, even if the driver is 100% paying attention and eyes were looking in exactly the right place where the child emerged at the right time, there is still reaction times - both in cognition but also physically moving the leg to press the pedal. I suspect that a waymo will out-react a human basically 100% of the time, and apply full braking force within a few 10s of milliseconds and well before a human has even begun to move their leg.