If you watch the video, the cat is unfortunate, but not particularly concerning. It was night time, and the cat ran underneath the car from the sidewalk. It's very unlikely that a human would do any better (though, I'd welcome Waymo adding more sensors to the undercarriage to prevent this in the future).

What is concerning is that a woman went up to the Waymo to try to get the cat, backed away a foot or two, and then the Waymo drove off. That seems dangerous, both for the fact that the woman was so close and also because her crouching down in front of the Waymo indicates that there's something exceptional about the environment so the Waymo should proceed with more caution.