Not to speak for everyone, but I was always taught to stay up on the balls of the feet, even when walking. Everything was about movement, except that I learned to be completely still until the attack. And even in standing still, we stood on the balls of our feet. Finding the stability of the whole foot was never addressed. I only made those connections after arguing with Rob John.
Huh. Interesting. I haven't encountered this before, but maybe I was just asleep that day.