I am EXP but also in GE. My bps have TSA Pre-check printed on them (even when I'm flying from foreign locations to the USA--except for one time I was randomly SSSSed).
From my understanding even if TSA Pre-Check is on your bp, if you don't get the 3 beeps, then you were not selected (for that trip).
On several trips out of T8 (JFK), if your bp had TSA Pre-check, the AA contract agents allowed you to proceed to the special line, but the TSA agent was only scanning every 3rd bp--but lots of non Pre-Check pax were also being sent to the Pre-Check, making the line longer than it should be.