When you watched my teacher in SF, you saw the advanced applications that he extracted from the forms. He explained the difference between application and even advanced forms. In his final years, he was very applications focused in his teaching. When he finally got to teaching an advanced form, he would tell us, "You already know the applications from this form. I taught you years ago."
Sounds like my Sifu.
Also, my understanding of waist punch is like RDH. Trying to find and use "Chinese waist" is not always consistent for me...sadly At 80 years old, Sifu Ly Hoa Yen definitely practices this and will call you out with "No powa! Body move arms!"
"The true meaning of a given movement in a form is not its application, but rather the unlimited potential of the mind to provide muscular and skeletal support for that movement." Gregory Fong