I thought the theory was to drill a neat hole, and tie up one or more buddies or corpsmen to rescue and care for the wounded.
A quick kill only removes one enemy.
On the matter of the FMJ 7.62, I had read that some Warsaw Pact ammo had a hollow in the lead filling, just at the point. Upon impact, the point would irregularly collapse, causing the bullet to tumble within the target..Yet it was still fully jacketed.
That theory was developed during the Cold War. It works when you are fighting an enemy that treats its wounded and doesn't simply abandon them.
Another problem is that the enhanced penetrator often doesn't wound them bad enough to take them out of the firefight unless you strike them in the head, heart, pelvis, or some other vital organ.