Stuff like checking the rear view mirror when slamming the brakes upon some surprise uncertainty, true. Humans will always be bad at this, but for a computer it's trivial to include the tail situation in the brake decision.
I think the issue is that basic ACC doesn’t understand intent and the larger picture. If someone merges in and I have control, I can usually just let off the gas a little bit, as they will likely speed up, or move out of the lane shortly. Actual braking is almost never required. But the ACC just sees some slow moving object inches from the front of the car and flips out to try and get back to a good state.
