I would think this is also simply bad structure for the proposed purpose. Whether you turn your feet in or not (like TWC), the purpose of the mah, in how I am taught, is in part to ram home the fact that everything starts, and ends, at the ground. My punch starts at the ground, when I deflect an attack some energy is still imparted on my body, this travels to the ground. If your knees aren't lined up properly with your feet, in the extreme manner you describe, dont you create a choke point for that energy and does that not then impart a "bad habit" of sorts? Now of course people will have natural issues, there is a fellow student at my school that due to a nervous system disorder has a severely turned in foot. You can compensate for that, to an extent, because it is a known natural condition. However training yourself to take such a position seems a different thing to me, though maybe their mah is serving a different purpose.