The classical (historical) definition of MB, as I understand it, goes something like this: The practice of Mula Bandha directly causes the awakening of the 3 1/2 coils of the serpent Kundalini, initially dormant at the Muladhara Chakra, which unravels its knots (3 and 1/2 coils representing the three Granthi and one last twist representing sublimation that lies beyond the three representations of the Guna), piercing the tailbone, up the golden thread of the Sushumna Nadi to the Manipura Chakra. If this occurs during an Asana class then I am surprised!
Ashtanga Yoga (as in the 8 limbs) begins with Ahimsa, non-harming. Yama is the first limb of the eight limbs and ahimsa is the first Yama. Thus ahimsa can be considered the base, the very foundation and support of the 8 eight limbs. Consider the use of the word ahimsa, the main root himsa, means violence, harm, aggression. When you add the “A” in front of it it becomes ahimsa, the opposite of himsa