I don't think it is all that complicated; EHLE has a 1250m long runway with on 1 side taxiways at equal distance which creates 4 grass segments. autorotation starts on final at 700 ft and normally ends somewhere on segment 3. It is normally a full auto with recovery into a running landing. They either ended at the end of segment 2 or at the end of segment 3 and tried to recover to go over the taxi way and land on the next segment. usage of the collective during the second flare, which normally starts around 100-120 ft is not necessary, at least I never used it in a flare and I did at least 100 auto's on a 3 bladed bird (H269). After the second flare we level ship at around 20ft or so and use collective only to cushion landing... It looks like the recovery did not work out with hard ground contact as a result, they pulled collective to pass the taxi way and then landed soft in the next segment. Question remains when did the blades hit the tail boom; after the first hard landing or during the second while giving aft cyclic to reduce speed while rotor rpm was already way too low....