I know a guy who survived being shot in the head, he says doctors told him only 5% of people shot in the head survive and less recover as well as he has (he has minor issues, you’d never know if he didn’t have a dent and some metal in his skull.) Sure you can easily hit an artery in the leg and leg shots are for sure deadly too, but I wouldn’t say head shots are less deadly lol.

The training to aim center of mass is mainly because it is larger, if you’re familiar with The Patriot you may remember the scene where Mel and his small kids shoot at the British, he illustrates this point by saying “Remember, aim small miss small.”

Aiming for a larger target means you’re more likely to hit the target, and yes in modern times it means you’re more likely to get proper expansion of a hollow point, which means you’re less likely to shoot through him into a bystander. It also does just so happen that the A zone contains the heart and lungs, which are vital organs much like the brain. Head shots are “more deadly” if you hit, center of mass is more likely to hit a vital area rather than miss simply by virtue of being larger.