My teacher would argue with your teacher. He would say that a stance with more weight on one foot or the other is inherently unbalanced, and therefore vulnerable.
The proposition is testable. Stand in hamni and have someone push on the middle of your chest, and then on your upper back. Experiment with different weight distributions and see what happens.
Assuming that Katherine is representing what she, her teacher, and other people drinking the same cool aid, would agree with regarding weight distribution and hamni, this statement may be revealing.
It is impossible to move without shifting weight from one foot to the next.
It is impossible to move quickly without lifting one leg, or both legs, completely off the ground.
All this internal magic stuff seems to equal not moving. What if the attacker has a knife? A sword? Multiple attackers? Multiple attackers with weapons. Sorry for the intrusion of reality.
As to what O Sensei thought about hamni, it is discussed in Budo. Assuming that people aren't going to argue that the translators failed to understand basic common words, we should be able to take what he said at face value. Also, there are photos. Looks like a pretty typical and modern stance, given his height, in even the old photos. If anything his stance narrowed, at times, as he got older (on video), which would contradict the arguments that the secret was learned from yada, yada, yada...