"Light as Heavy" and "Heavy as Light" are advanced force application techniques. After comprehending these, it is beneficial for understanding the subtleties of the Hua Realm, thus advancing to Refining Internal.
Before Refining Internal, it's like forging iron, refining the impurities of one's martial arts. After Refining Internal, it is about gradually melding all aspects of one's martial arts into a single furnace, like alchemy, perfecting one's cultivation and thus achieving the status of a Martial Arts Grandmaster. Only then can one truly stand on the shoulders of predecessors and continue to forge a cultivation path suitable for oneself.