Reading the report it seems more basic in that the pilot may have expected his control column inputs to disconnect the autopilot as per more sophisticated APs.
It was implied in the report that how to disconnect the autopilot may not have been fully known by some pilots/operators. Remedial actions included the operator revise their SOP to explicitly state AP disconnect methods and to incorporate it into their Type Conversion and Recurrent training.
It's interesting though, how would most pilots instinctively expect an AP to function when say, after having converting from a type with a more sophisticated AP to a less sophisticated AP or vice-versa?
Further, the design sounds a bit contrary.....it has sophisticated FBW, no mechanical trim-tab elevator control system but mated to an AP with only basic logic/functionality that ignores most of the flight control inputs the pilot is making?