Lyman,
No, N1 was reduced for turbulence penetration by one of the pilots in anticipation of turbulence ahead. I asked PJ2 the question about how this is actually done, moving the throttle levers or another way. It was a pilot initiated action to slightly slow down.
IMO, the A/P was doing what it does, making corrections for ups and downs. At the point of disconnect, it was correcting for an up and therefore the nose was down. From there on, what took place was pilot input. There was nothing wrong with the aircraft or its systems. The reason the A/P disconnected was UAS due to pitot icing, not turbulence. There is no evidence to support the "severe" turbulence theory, but plenty of evidence to support the pitot icing. In fact, I think that will be the #1 issue Airbus will address going forward. I think you will see some technological advances, perhaps on the A320Neo or even the A-350 if the program slips more.