Kmark thanks for the update on FDM.
I do not agree with your simplified assessment for the reason for the crash – the propellers entering beta range. Both props did go into beta and the aircraft descended, but it appears that at some point the left prop was recovered to the normal range (it was found to be in the feathered position). The FDR stopped at approx 900 ft agl when both engines were stopped.
Thus, as a hypothesis, as we cannot be sure, the aircraft could still have been flown with the right engine shut down and the left working normally. The airspeed remained high, thus there should not have been a problem with control (Vmca/Vmcl). The flaps were retracted to reduce drag. The unknown was if the left engine would have produced enough thrust to over come the drag of the right prop in reverse.
I agree with ALF5071H’s post on 16 Dec. The report confirms that both engines had been shut down, and if a shut down is the logical drill for an over speed, for which there is no evidence that the crew detected or that a drill exists, then only the right engine should have been shut down, certainly not both at 900 ft. No explanation was given in the report as to why both engines were stopped.
For at least one engine this appears to be ICR after a crew induced PSM.