There are some unknowns here. I have not been able to discover what AP following distance setting the Chatham people used. From the video i am estimating that it's a little under 2 seconds. If the Tesla had been following with a 3 second gap, the vehicle would have probably stopped before hitting the dummy vehicle. When using AP1, I generally use the longest distance setting which allows me time to decide and act. I generally do not have a problem in front, but from behind where if the vehicle is too close, and AP will slow down too quickly for that driver to react.