Well, I heard a shihan who studied with o sensei say that Ueshiba Morihei refered to standing with the feet closer than usually taught today as a "stance of heaven and earth".
So my question is wether there may be an "advantage" in terms of IS.
Thank you for your detailed explanations!
To answer your question, yes, IMO, for reasons that Lee has explained. However, i still have not heard a narrow stance referred to as Heaven and Earth - however, I have heard the term Heaven and Earth used when referring to the balance of yin and yang within the body, which is core to IS