We differ on what being "knocked down" means.
Generally on this and other forums the term knock down power is understood that the person using it believes in the Hollywood description with the victim flying through the air. Or at least being caused ti fall back, and down strictly by the kinetic energy of the bullet. which you agree is total BS.
But of course you are free to use the term as you like.
I even heard a guy with no business behind the gun counter at a local BPS tell a customer he should buy a 45 rather than a 9MM because it has better knock down power, and "With the 45 you can knock somebody down even if you just hit them in the finger" I didn't say a word, just make sure if I'm looking to buy from them he isn't working the counter!