in the AA New York accident the rudder was being solely manipulated by the pilot. It was pilot error that generated the rudder input. The system had nothing to do with it.
On AA's A300's there is no data input from the rudder pedals. The DFDR records rudder movement only. Because the FO was the PF, it was assumed that the rudder was moving on his command.
Also, the DFDR traces were such a mess, the NTSB never published the raw traces and they had to cook the data in order to make any sense of it. This is partially due to the type of recorder the aircraft was equipped with which sampled rudder position at a rate of 2 points per second. Those units were later de-certified.
I am not summarily condemning the A300 in this accident, however I can say with confidence that the investigation was not among NTSB's finer moments.