Nobody claims they aren't different monsters according to the rules. That doesn't mean they aren't the same monster in our shared modern fantasy fiction. Some may be more skilled or dangerous than others but the dichotomy of the "low level" ogre having over a hundred HP vs an ogre with far better AC and hits for far more damage having 1 HP is incongruous to a lot of people.Keep in mind that with 4e D&D, "just an ogre" isn't really a thing. The "ogre" is represented by a variety of different stat-blocked NPCs: ogre thug (minion), ogre bludgeoner (minion), ogre savage (brute), ogre skirmisher (skirmisher), ogre warhulk (brute), ogre cave hunter (lurker), ogre ironclad (soldier), ogre storm shaman (controller), and ogre dreadnaught (soldier). In this way, they operate more as specialized units instead of some sort of platonic or static idea of "ogre."