ORIGINAL: Bob H in NH
My understanding is that it allows a little downward pressure on the arrow during the draw and shot to keep it from "bouncing" on the rest.
The same can be accomplished with a tied nock point below the arrow, then tie the loop below the nock and above the arrow.
--Bob
This is what I have been told as well..........
Now I simply tie in a nock below the arrow and the loop below the nock and above the arrow as Bob said above.