I heard something about the strategy of incapacitating an enemy vs killing them, forcing enemy soldiers to attend to the wounded. Not sure if true, but if I was given a .22 cal weapon that was designed to injure people who were trying to kill me with .30 I would be pissed, so if that was the case the designers might not want to own up to it.
That assumes the enemy is going to stop fighting to help a wounded comrade. Can't count on that.
Also, a wounded soldier can be patched up to go fight again. How many times do we have to wound him before he kills one or more of us? Not a good plan. It would make more sense to shoot low to wound someone if you want to force others to carry them rather than issue less lethal ammo.
I think many of these stories are used to justify the lower lethality of the smaller round compared to the 30 caliber family. If most states won't let us hunt deer with them, obviously the lethality is subpar when targeting humans.
Then again, if you look at the kills and injuries inflicted with AR-15s in mass shootings, it's obvious that the weapon is not anemic regarding lethality. I submit it's all about the operator and the environment (i.e. distance, protective gear being used by the enemy, etc.)
Just thinking out loud. I have no actual combat experience, and hope I never do.