Sometimes the investigators have a very difficult task- some wreckage found a year later, no witnesses, etc. This is not one of those cases. There were many witnesses and video from many angles, including inside the cockpit. When the AAIB report states the Hunter "appeared to be responding to the pilot's control inputs" they are basing that on a careful examination of the video, particularly the video from inside the cockpit. The phrase "appeared to be responding to the pilot's control inputs" speaks volumes.