I always find it interesting when people invoke design intent as if it was the be all to end all of arguments for how something is to be applied. The goal of design intent is for the designed items to meet the parameters of the intent, but the design may meet the parameters for many things not intended, like kevlar that was intended for use in vehicle tires. It was NEVER intended for use in ballistic vests, ship sails, boat hulls, rope, etc., and yet it is excellent in those applications as well...things the developer never ever intended.
Since we are talking about a cartridge, 7.62x39, it does not care what it was intended to be used for. As for the bullet flying down range, it doesn't care either. Of course, the Soviet intent was with ball ammo. You load and fire the same bullet from a different cartridge at the same velocity and it is no longer 7.62x39, but the down range performance will be the same, right? The cartridge doesn't do the killing. The bullet does.
Last I checked, humans are animals and the Soviet military has been hunting with the 7.62x39 since it was issued.