The Traditional Stance of MMA (And Other Combat Sports)
It's about the rotation and/or transference of weight that got you there. A stance means nothing without the context of what led to the momentary posture. When you bend your front leg and straighten out the back one for Zenkutsu-dachi or Gōng Bù, it can simply be for a brief moment in order to properly launch a powerful strike with structure.
Source: blackbeltmag.com