Funny thing here is it's not corrct to do that either. Because some attack/health values are better than some others even though they may be lower. For example, 4 attack is vastly superior to 5 against Priest, and 6 is vastly superior to 7 against all classes, because of certain cards which affects enemy minions with a minimum attack value of 5 and 7 respectively.
So War Golem (7/7 for 7) is a lot worse than Boulderfist Ogre (6/7 for 6).