JD, I don't think training a 15 sec wait for a stall warning at altitude is a good idea. I used to teach stalls and spins, albeit in small trainers not in large transport aircraft. To sloppily quote Mr Davies --" if you have a choice between being stalled and something else, choose something else."
The first indication of stall warning ought to clue the pilot to decrease AoA, even if slightly, and cross check immediately what to do next. If the stall warning is determined to be spurious later, then recover, reestablish flight condition, and press on.
Do nothing for 15 seconds? 15 seconds is enough time for a stall to turn into something worse. Depends on flight contitions and configuration.