Eeeeeh, it kinda makes sense to me. If the "break angle" is steeper, when the string is tugging up away from the sound board, I could definitely see how there would be a more efficient transfer of energy. Of course the strings are not just tugging up. They're moving all around so the exact mechanics of it is not trival. I suppose the guy could just be talking since he doesn't provide definitive proof of a result.In terms of vibration transmision, it doesn't make much sense. It would if the materials were of very different density or hardness.