Part of the PreCheck determination for an individual passenger is the product of an analysis of passengers and passenger data related to previous flights that may go beyond the single ticketed PNR to be flown by the passenger on the pending flight.
The US wanted (and sometime got) this data before but wasn't being voluntarily given it to the extent wanted under formalized agreement.
By agreeing to accept PreCheck, the EC is recognizing that some privacy right waivers may be observed by them too.