TC you are right, there has been much drivel in this thread, a lot by people who have only a passing acquaintance with Engine Off Landings - the suggestion that you can complete an EOL (that doesn’t trash the aircraft) without using collective is my opinion ridiculous for the following reasons:
In autorotation the blades are kept rotating by the middle section of the blades – the root has too high an AoA and is therefore stalled, the tip section has a low AoA and whilst both produce lift, they also produce high levels of drag which put the total reaction facing rearwards (effectively slowing down the blades).
The flare moves the driving section of the blade outwards as the AoA is increased – the net result is an increase in rotor thrust and rotor RPM.
The flare therefore reduces RoD and forward speed but only while the AoA is being increased – once the flare is stopped the RoD will build up again because it is the air moving up through the blades that provides the driving force.
So in theory you could flare the aircraft from say 100’ all the way to the ground and you would (if you were gentle and progressive with the flare) continue to reduce forward speed and RoD to touchdown. BUT what attitude will the aircraft be at this stage – rather enormously nose-up I would suggest (not a great way to land anything except the space shuttle). Therefore in order to survive the landing you must level the skids/wheels/fuselage attitude – OH DEAR you are now reducing the AoA (negative flare effect if you like) so the rotor thrust and Nr reduce rapidly (try bunting in autorotation and see what happens to the Nr) just as you are accelerating the fuselage about it’s C of G towards the ground.
This is the point where you need collective to use up the remaining energy in the rotors to generate a short-lived, once-only burst of lift (and all the drag that goes with it and slows down the rotors) to cushion the touchdown.
I have stretched an EOL many times after the flare by selecting a level attitude and gradually milking the Nr as the aircraft sinks towards the ground – is this helped by ground effect? I don’t know but anything that reduces the drag on the blades that are trying to slow down, must be a good thing.