[moo-mop]

The physics of arrow flight is more complicated than nodes (arrows have nodes but don't quite fly like that classic description you often see when they line up). However, yes, as I understand it basically the idea is that ideally the arrow comes out of the bow travelling, on average, in the way it is pointing. Therefore, as the button will depress, in order that the arrow is being pushed along that direction you need to have it outside the string. As to how to get it just so and how much difference it makes anyway I've seen no evidence.