Devil's Advocate: You already knew what to look for* when you watched the video. I would say that a typical driver in the same scenario certainly wouldn't have had nearly as much of three seconds between noticing and collision.
Edit: *Specifically, to be on the lookout for a black sideways truck on an unlit road directly in ahead of where the car is traveling.
If a kid running out to get their ball is a the standard example of a hazard that drivers should always be expecting on a residential road, I think a broken down vehicle is the standard example for a highway.
Maybe a human could have braked even a little bit, but the autopilot didn’t brake at all. That’s a problem for advocates for it