I believe it was Dave Calvert that started the concept for windsurfers, before he started designing multihull sails.
The theory is you have a fuller, more powerful area of the sail up high for lighter winds.
Now, when a puff hits, because of the length of the batten sticking out from the upper mast, the wind uses that leverage to allow the top of the sail to blow off to leeward, thus depowering in the puff, lowering the center of effort, and also reducing the heeling moment.
Sort of an automatic transmission, it shifts to a high gear in the puffs, and when the puff subside, it shift down again for more power.
Add to that the ability to downhaul and it becomes even more useful.
And they definitely work much better than pinheads
Rick