You're omitting the context provided by the article. This wasn't just a random scenario. Not only was this by an elementary school, but during school drop off hours, with both children and doubled parked cars in the vicinity. If somebody doesn't know what double parking is - it's when cars parallel park beside one another, implicitly on the road, making it difficult to see what's beyond them.

So you are around young children with visibility significantly impaired because of double parking. I'd love to see video of the incident because driving 17mph (27kph for metric types) in this context is reckless and not something human would typically do, because a kid popping out from behind one of those cars is not only unsurprising but completely expected.

Another reason you also slow way down in this scenario is one of those cars suddenly swinging open their door which, again, would not be particularly surprising in this sort of context.

That's my thinking as well. Taken in some abstract scenario, all those steps seems very reasonable, and in that abstract scenario we can even say it would do better than an average human would. But that is missing the overall context that this was an elementary school during drop-off hours. That's when you crawl at 3 mph expecting kids to jump behind any car, and not going at 17mph.

Driving is based so much off of feel so my numbers may be off, but in the scenario you are talking about 5mph seems reasonable, 10mph already seems like to much.