Peng is not Peng.
I revisited this point with my student. Peng the expansion principle is too often confused with Peng the upward force vector even by famous and experienced masters who should know better.
The consequences of this confusion is that one ends up having to muscle out the opponent rather than truly use the ground reaction force to uproot and unbalance the opponent. You can see the symptom of this misunderstanding in the way “masters” lose their balance after doing fajing or in the way their arms tremble and shake when encountering resistance.
Peng the jing is like a wave lifting up the opponent from underneath; this is all too clearly alluded to in the song of Peng. Fortunately, my student had recently been to a beach and felt what it was like to be lifted up by an actual wave.
But just in case he didn’t get it a demo to differentiate Peng the principle against Peng the jing was in order. After this, I have no doubt he will now understand why Peng the jing is used for attack and defence rather than Peng the expansion principle.