Spiral movements tend to take up the slack in fascia without tensing muscles. This means that they make progressive connection from one part to another to another all through the body. This progressive connection allows each part to be separate but also in relationship. It is a democracy in the body rather than a tightly bound way of connecting (which muscular binding tends towards) which is more fascist.
Babies learn this progressive connecting through the act of rolling. In this video, Teresa demonstrates helping someone to re-enact the development of rolling. Since in this culture this progression is often blocked in the pelvis, she starts by doing proximal movement of the pelvis.