Precheck for non-member companion?
I've had TSA PreCheck through my NEXUS/GE membership for about 4 years now. In the past 1.5 years or so I have been doing a lot of travel with my girlfriend, and have noticed that whenever we are on the same booking/PNR we both get PreCheck boarding passes, despite her not being a Precheck member. Not only is she not a member, but I believe she is not even eligible for the program, as a Chinese citizen in the US on a student visa...
I know TSA used to run a program where some individuals are randomly selected to be given Precheck on their boarding pass (managed inclusion I believe was the name of that program) but my understanding was that had stopped. FWIW I also have quite high confidence that my companion getting Precheck is not "random" but specifically linked to being on the same itinerary as me: after over 30+ flights together my girlfriend has had it 100% of the time, and 0% of the time when we travel on separate bookings, and 0% of the time when she has traveled alone.
Is this a known "benefit" of the program? Have others observed the same kind of behavior?