You can bet they were descending at near minimum clean speed the significance being they were above FL200 where minimum clean speed is not displayed on the PFD.
Entered the hold, thrust at idle (speed on elevator) autopilot possibly reduced the bank angle to protect itself from the slow speed thus didn't follow hold, crew disconnected rolled pulled G and bingo stick shaker. Thrust takes time to advance from idle to something decent at high altitude. Crew does stall recovery maneuver.