I'm not sure it matters, because going from disengaged to fully engaged and actually breaking to a stop in 1.3s is not happening for an average human. By the time the system alerts the driver, the ped is already dead.
But an attentive human would have noticed the pedestrian around the same time the system was confused, ~6s before impact. Enough time to swerve and stop.
At 6 sec before impact the driver for sure would assume the system will notice and brake in time. Until the driver realizes that the automated system will NOT brake its very likely too late. Automatic systems which rely on humans braking in time have no place on the street, imho. This may be different for lane assist where malfunctioning is more obvious and leaves more time for intervention. Although even in this case the latest Tesla accidents may tell a different story.