The Windcutter allows you to do a couple things that you could never get away with a longer belly line or other stnadard shooting head type lines.

With the Windcutter allows you to get away with a poor setup and poor hand placement.

I can come around very low with my hands and throw an awful D-Loop with the Windcutter and yet I will have no problem firing 60 feet if I apply enough power on my forward stroke...if you come around really low and throw a shotty a D-Loop with a longer belly line, you will have a hard enough just throwing the belly, let alone shooting 10-30'.

Also with a Windcutter I can get away with the flying butt syndrome in which I bring my lower hand way out which in turn drops the tip to an almost 9 oclock position...I can still throw 50-60 while doing this with a Windcutter...I could never do this with a longer belly line or even some other standard shooting head type lines.

By learning on a longer belly line...you learn to come around much higher with your hands (what Derek Brown calls the shotgun lift) and throw an accelerated D-Loop with just the right amount of line stick.

I hope that makes some sense...