They are both gaming the game.
Perhaps, but there is a vast difference in degree. Running two or more accounts for the same side offers no advantage for either of the accounts. Having the second account on the other team for either spying purposes or padding the score of one of the two accounts is detrimental to fair gameplay and certainly puts one who may be going for a legitimately good rank/score at a disadvantage.
Put another way, I really can't see how anyone on the opposing team can be "harmed" by facing two opponents controlled by the same person. It would be no different (one could argue even easier) than facing two opponents controlled by different people. However, at the very least anyone going for rank is "harmed" any time someone uses a shade account to pad his score.