I mean, you're right; someone making that list might not think to include "centaur", and maybe one Halloween a child is dressed up as one, and the computer vision system interprets the "centaur" as a horse instead of a child, and it makes the wrong decision, but how many centaur-related accidents do you think self-driving cars are going to be involved in each year?

It's completely feasible to imagine writing a list of the top, say, 100 things in the world that a car needs to make morally-significant decisions about, and then deal with every other accident or near-miss after the fact. Interactions with unrecognised objects should be rare enough to be a rounding error when comparing accident rates between autonomous and human-driven miles.

We're really lucky we never see more than 1 thing at a time on the road.

You don't think self driving cars categorize and prioritize things?