One other thing - wouldn't this airplane have had to do a "Double Rudder-Kick Test" during flight-test?
I would think so, but not in wind gust conditions.
The rudder kick and reversal maneuver done by AA587 would have been OK at a steady airspeed - it wouldn't have exceeded the limits imposed by the flight control system.
But it apparently encountered a situation where the rudder was permitted to travel too far - my hypothesis was a wind gust or wind change of direction that caused the high rudder angle (allowed at lower speeds) to overload the rudder and vertical tail.
Once the tail comes off, the "flat spin" of earlier posts would be ongoing until gravity wins -- the yaw control of ailerons is not sufficient at takeoff/climbout airspeeds.