It is a bit complicated to explain but generally it is the idea that to learn something you should practice with EXTREME variation with a consistent goal. The differential learning people say that practicing something on the perfect path of what you want to learn simply doesn't work (it makes you better while you are practicing but you end up retaining NOTHING) and you should actually practice on the extreme ends of the goal and make your brain find a motor solution to these extreme problems. The brain will then learn the most efficient way to do the task and it will better learn the task even without difficult variations. The retention is very high as well.
This PODCAST explains it better.
The creator of differential learning is Dr. Wolfgang Schollhorn who I have corresponded with a bit. He has helped a lot of soccer teams in Germany and Portugal and I think Shotput and Speed Skaters as well. Very little with golf from what I can find. I sent this message to him. It is my idea of how to use differential learning to improve a full swing.I am waiting for his reply.
THANKS FOR WATCHING. We are putting some effort into incorporating this into a future Be Better Golf School.
If you would like more info or have a suggestion on a location. Let me know