Without anything specific to go on the only thing I can put forward is that shifting between stances can allow you to perform certain techniques.
It works best for me when you program combos into your body and know what position your body is in when one ends so you know which stances you can blend seemlessly into from there. Clumsy and obvious changes of stance must be avoided or reduced at least cos they will create more problems than they solve.
But all that faffing about will prolly piss of your MT instructor anyway!
