Your statblock is not absolute in any real way. It changes all the time. There's an entire leveling system that changes your statblock routinely. Never minding things like level drain, magical/mundane enhancements, situational modifiers, etc.
And mechanical symmetry is a myth. It's certainly mythical in AD&D. What is the wisdom score of an orc? How much experience does a dragon have? How, exactly, does an orc suddenly gain a boatload of HP, Strength and attack bonuses the second he becomes a chief? What if that orc chief is young or old? On and on.
Statblocks are an abstraction of a snapshot in time. Your statblock might be X right now, but, tomorrow, it might be Y. And, again, 4e D&D was very clear on the notion that the mechanics were absolutely NOT meant to be used if the PC's were not present. If you're applying cats to minions, that's your fault for not using the system as written or intended.
Never minding that in AD&D, an ogre can have 5 HP. Looks like a minion to me. Let's not forget, as well, that a 1st level fighter can kill an AD&D ogre in one round without too much difficulty. Weapon Specs and a longsword is 28 points of damage in a single round. More than enough to kill most ogres. Add on a percentile strength and now Mr. 1st Level Fighter can quite reasonably kill an ogre in a single round.