This is a quickie to help everyone correlate throwing punches with the dynamics of athletic throwing, in particular the discus.
In the video the mention to separation and stretch reflex should not be something to cause concern, they are present every time we defend and attack even if we are not aware of it.
Pay special attention to the weight shifts and the torque creation, in physics talk this is the summation of forces at play, and it translates to power.
Observe how the upper body balance is conserved even as the lower body is dynamically mobile, and then observe the weight transfer as the athletes lower body stops causing immense acceleration of the upper body in the same way that a Trebuchet works.
In the discus the sinking and rising is really quite pronounced, but sinking and rising is an inherent part of both Chum Kiu and Biu Gee, just much subtler.
Relate this to your Knife and Pole forms to get the most benefit, then go hit something.