I would not say the 5.56 was chosen for that reason but it is an entirely valid military principle that enemy with incapacitating wounds are a far better result than straightforward kills.
A dead man is a dead man, he can be dealt with later, he has no immediate needs. Wounded men have an impact much deeper in the purely logistical sense. Each tying up a long strand of resources in men (a dozen? can't remember the figures) and materiel to evacuate them from the battlefield, give treatment etc. Wounded men cause greater attrition than the dead. Grim; but accepted within military thinking for hundreds of years.
Cheers
Adam.

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