It is an optimised balance between standing strong rigid (wide stance) ....
I don't think I would emphasize the "strong/rigid - element" in our hanmi. We don't try to "hold the ground" by using a certain stance/kamae.
It' more about connecting with aite, and leading one's own and also his feeling down, using this connection.
Do you sometimes do a technique just standing on one foot? You don't need a wide stance to be centered and grounded.