Derfred point taken regarding the origin of the reported turbulence. Passenger reports of turbulence are not inconsistent with the ATSB statement of airframe buffeting but the two are very different in origin. I could imagine that a distracted crew would experience a fair bit of a WTF moment if their first indications of a problem was buffeting and the stick shaker. They would have realised that the aircraft was about to do something nasty and reacted accordingly.
A significant application of forward elevator would have resulted in the chaos down the back of the aircraft as reported. Not dissimilar to the A330 incident off WA where a sudden nose down pitching manoeuvre led to injuries in the rear of the cabin.
Completely agree with your last statement.