Brazo's explication is similar to how tai chi is applied while standing. Sinking of the joints, "emptying" and "rooting" (stances) is how this is effected in that system.
You see the general concept across martial arts because all genuine martial arts reduce to "physics and physiology".
It means to create a rigid posture with your limbs against the opponent so that when they push against you your arms/legs do not collapse, closing the distance, but remain straight.
This is analogous to the "frame" of e.g. the legs of a table, which support the weight above it not through active effort ('strength'), but by their inherent rigid ...