Earlier quoted context omitted.
A randomly stopping car is dangerous even to people who aren't tailgating. A human would be charged with dangerous driving for that - which is a felony in my jurisdiction.
Both behaviours aren't great, but the at-fault driver would be at the back. Even though the stopping frequently randomly is likely more dangerous.
More importantly for discussion of an automated system shadow braking, however, fault of drivers based on negligence (or more serious mental states, like recklessness) is a separate concept from fault of manufacturers for product defects (which is based on strict liability, not negligence, and therefore bars to liability based on negligence of the injured party due to contributory or modified comparative negligence theories would not generally apply; liability might be barred on a theory of superseding intervening cause, but that would require the intervening cause to be unforseeable—too close freeway following is not so rare as to be an unforseeable intervening cause and thus would not usually limit recovery on a strict liability product defect claim.)
[0] see, e.g., https://www.nolo.com/legal-encyclopedia/is-fault-automatic-r...