See, but that's the thing. Is that a design goal for simulation? If entities in the game should have a consistent mechanical simulation, doesn't D&D rather fail in that regard? After all, the PC's are not consistent, at all. There is a massive difference between a 1st level character and a 20th level character that is far beyond simply becoming a better swordsperson. And, if we look at other systems where simulation is a goal then we do see that entities in the game do have consistent mechanical representations. After all, a GURPS character does not change very much over the course of its lifetime. A Traveler character doesn't become ten times tougher over the course of its career.
Not only that, but, in most versions of D&D, entities are not consistent. There's no such thing as an "orc" in 3e D&D. Doesn't exist. Every orc is based on an NPC class which means there is no consistent mechanical representation. Thus we get 20th level orc smiths that are more powerful than trolls, despite the fact that an orc is weaker than a troll. None of the humanoids in 3e are consistent because humanoids in 3e are represented by classes which are based on the level system, which is not consistent. My orc smith becomes a better smith by killing goblins? How does that work?
Even in AD&D, there is no real consistency since being a leader of orcs suddenly grants me significantly more HD and HP. Does that mean when an orc leader is killed, another orc suddenly hulks out and gets 4 times tougher?
This idea that D&D has ever had consistency in mechanical representations is not true.