Somewhere in here he explains the longer handle. Part of his course is that you have to make your body last by working smarter not harder. The real answer is how you grip the handle. Thumbs pointed in the direction you are working which sets the shoulders for optimum leverage and muscle use.
I'm a recent convert to the long handle, no-grippy-thing-on-the-end, shovel. and my back has reaped the benefits.
Standing upright and holding the handle near the end means you can't lift as much dirt, but it means you can lift those smaller amounts all day, and all the next day! Rather than in the past with the short handled shovel when I would lift large amounts all day, then decide it would be best just to stay in bed the next day...
Occasionally, bad habits will creep in and I'll find myself inching down the handle to pick up just a little bit more. So I chastise myself, and move to the end of the handle. Practice makes permanent, and one day it will just become habit for me.