The check step was trivial
Sorry PBL disagree. The check step was vital in ensuring airworthiness was maintained. Without this critical step one can only assume airworthiness was maintained. The check step as far as I am aware was to test the Air data system. The AD itself states:
A persistent erroneous warning could confuse and distract the flightcrew and lead to an increase in the flightcrew's workload. Such a situation could lead the flightcrew to act on hazardously misleading information, which could result in loss of control of the airplane. This action is intended to address the identified unsafe condition.
United got lucky nothing more nothing less and trivia belongs elsewhere.
Had an aircraft had an accident immediately after the modification because they were distracted by a persistent erroneous warning the attitude towards that trivial matter of testing the system would be totally different.
System integrity is fundamental to airworthiness after a modification. United have a duty to fare paying passengers to ensure that to the best of their ability the aircraft they are flying in is safe. They failed in 96 cases X number of flights.
I hope this is one of the largest fines ever.