Button combos were considered 'cheating' because they gave the player an advantage. There is no advantage here because every single Last Word has this problem. It would be different if you had to press a series of buttons to get that damage but you just shoot. A more viable argument on your behalf would be the NLB animation canceling button combo, which if done correctly skips the cocking animation on the NLB. But I don't see you complaining about that.