Sounds like Etihad wants to do something to make sure that their AUH-US pre-clearance flights depart on time.

From what I heard, these flights often get delayed due to many passengers being subject to secondary customs screening (US customs x-rays the bags and if they find items of interest [organic material such as food etc.], bring them upstairs for further inspection with the passenger present and then send the bag back downstairs for loading onto the aircraft).