I believe I originally learned this through my teacher Jill Miller, and later Paul Grilley. It has helped me become much more stable in all my arm balancing, handstands, planks, and downward dogs. I had been told for many years to turn the hands out in Anusara but it was never made clear why. As many of us know, when we understand the why then we will often put our hearts into it-whatever it may be- in this case all postures where hands are weight bearing. Hope sharing this helps you.