Footnote 4 in the NTSB letter catches my interest:
"Preliminary information based on FDR data and an analysis of the manner in which rudder position data is filtered by the airplane’s systems indicates that within about 7 seconds, the rudder traveled 11° right for 0.5 second, 10.5° left for 0.3 second, between 11° and 10.5° right for about 2 seconds, 10° left for about 1 second, and, finally, 9.5° right before the data became unreliable."
These are the last 7 seconds the fin and rudder were well enough attached to give reliable FDR readings. The FDR shows FOUR complete rudder reversals inside "7 seconds" but the sum of the intervals given only comes to 3.8 seconds and we are not given the travel time of the last rudder movement to the right. The letter does show that the last reliable FDR reading shows the a/c in a left yaw of 8-10° and that that combination exceeded the structural strength.
We are only given the last yaw angle -- I would really like to see yaw vs. rudder position in these 7 seconds. In my opinion, the crew would have to be Tour de France material to work the pedals that fast against a 32 pound force. This inclines my suspicions to the flight control system.
In traversing the two wake vortices, it is possible that local effects confused the yaw damper sensor system and resulted in counter-corrective rudder movements.
I am tempted to propose an expensive and hazardous experiment with a 747 and A300 flying the accident flight profile in a remote area with an unfiltered FDR -- remote control or ejection seats for the A300 crew highly recommended.