Hughes500 - that could well be true about the 53, it has a very high disc loading and therefore a powerful and fast downwash. they were probably talking about a vertical descent from a free air hover where the downwash would be at its maximum rather than a quickstop where flare effect is giving you relative airflow from beneath the disc and also masking your real power requirements.
However the 412 is nothing like as heavy nor has such a high disc loading - it is possible he just ran out of power but there isn't any noticeable Nr decay (well to my ears) - I think we can all agree it was a very poor piece of piloting whatever happened.