I read on https://expediteq.com/index.php?option=com_sppagebuilder&view=page&id=18 (mirror):
A car can only use the SENTRI lane if all passengers (including children and infants) have a valid SENTRI card and passengers have nothing to declare at customs.
Since the vehicle occupants must declare anything they bring to the US, does that mean passengers can't bring their own luggage when going through a Sentri lane?