I think he says stuff in certain ways to get a rise out of people. I am retired from pathology now and can say that I examined all calibers of bullets from people both alive and dead. All of them killed someone and all of them did not, including the .22LR. The bullets all looked the same too. FMJs intact or distorted, hollow points opened to varying degrees.
People forget you are taking a fixed object (bullet) and shooting it into a variable object (body) so should expect some mileage may vary. The diameter difference at either the start or finish is not enough to matter enough to waste time thinking about. Remember the body has survival mechanisms built in. Skin is elastic so wants to close any hole made by any object. The organs themselves have a certain amount of mobility inside and are made of different tissues with different densities etc.
Police depts. have reported no real street use differences among the calibers whether they issue them all or went back to the 9mm from .40 or .45 using modern ammo in all calibers. It's still where you shoot them first.
You need to have confidence in the gun, caliber and ammo you are using. That maybe the most important factor in you surviving a gun fight?!