I think we are getting pretty close to the facts on this interesting thread, but there must be an INCREASING ground effect at the end of the level off-phase. This is because we are increasing pitch at that point - which puts us aerodynamically closer to a normal IGE hover (air is moving from the top to bottom again). I am talking only about the very last phase of an touch down auto. In big helicopters that phase can actually last quite a bit.
sp