Going from the data in the report the aircraft lost 2,875 feet in 22 seconds, skydiving reckon on ten seconds for the first 1,000 and five seconds for each following 1,000 ie 19.375 seconds for 2,875. We might then theorise then that the aircraft was in freefall, and mast bumping being responsible for loss of the rotor. Examination of the main fuselage/main gear box/mast would reveal all. The physical state of the tail boom might suggest an inflight separation, which generally points to a mast bump episode, time will tell.