I think the point of the woman in the first video was trying to say that keeping your hands wider apart will cause you to have tension that draws from more proximal parts of the arm to the upper body. She neglects the idea of wrist strain and fatigue, which is the reason why most RSI sufferers move to ergonomic keyboards. Workstation ergonomics (desk, chair, etc) is just as important as the type of keyboard you use, so im not sure that I would take that video seriously.