Dave
Dont forget not only does the flare at the bottom reduce your rate of descent, it also reduces your forward speed to next to 0, but it also increases rrpm considerably ( loading the disc) This increase in rrpm means you have to check the disc to stop it overspeeding by pulling pitch, this futher decreases momentum of the ac.
Cant see how you would get vortex ring in a normal auto unless you were doing min fwd speed one and pulled the lever to max pitch at about 10 ft, even then there would be no time for the state to build up as you would be on the ground !!