So I just came though TSA pre at DFW D and on to my AA to LHR and the only time i needed a boarding pass was to access Flagship lounge.

Both security and at the gate all they asked for was my passport.

is there some backend magic now that ties up pre flight info provided to AA to my passport number?

Visions of being offloaded for ‘not being at the airport’ having not scanned a BP at security but seems there’s some magic going on!