Clipping hackle is nothing new to fly tying. Here are a few examples of how and why I use the technique, and how it affects several similar patterns in order to effectively fish a particular hatch.
For the full video please click on the link below:
I have V-notched hackle for many years. To me, it more closely mimics the actual insect with its legs out to the sides - not directly underneath.
If I were to place a V-notched fly on a surface, the fly would lie pretty flat with the body pretty much also resting on the surface.
And that is pretty much what the video shows. Some more than others. 
Plus it takes into account the tailing and body material as well.
Changed the link for the video, some could not connect.