There is a line in Autobiography (maybe chapter 12 ) where Yogananda says that Sri Yukteshwar could have been a mighty warrior ( or words to those effect ) if he chose but that in this life he chose to defeat the inner warriors ( or words to those effect ) and to storm the "inner citadels whose fall is the height of man". I was just wondering what he was referring to by that last bit. Was he referring to how far we drop from crown to base chakra in the physical sense?
The full quote is "He had chosen instead to storm those inner citadels of wrath and egotism whose fall is the height of a man.”
I’m not aware of any explanations that Yoganandaji may have offered. He might well have meant what you said (the descent of energy into the reservoir of kundalini energy near the root chakra), even though that distance is, technically, less than "the height of a man." I have always assumed that he intended his comment more metaphorically (i.e., simply to break down the fortress walls of ego).
Either way, however, the meaning is the same: He incarnated to help others find God.