I agree that no bullet knocks a man down by energy, any more than it does a deer. A deer goes down based on what part the bullet hits.
There is a thing called “Momentum”. How fast is the energy of the bullet transferred to the target. I shot a doe with my 12 gauge broadside in the engine room with a 3 inch 00 mag. a few years back from less than ten feet. She just stopped midstride and fell down. I suspect that the same impact WITHOUT penetration to spread the impact out over time, such as if she had been wearing armor, would probably have knocked her off her feet.