Trying to wheel this thread back around, and avoid the low level edition warring that seems to be brewing here.
I look at a simulation as a model for describing what happens when you do something. Newtonian physics might be an abstraction, sure, but, it does describe pretty well why someone might yell at me from across the room when I break wind, even silently. (Well, it might be Newton's fault, or it might be that bean burrito I had last night, or possibly a collusion of both.)
OK, but that's about results - not necessarily about the process by which you arrive at those results.
In any case, a simulation model in order to actually BE a simulation model has to tell you how something happened. And we do see this in arguments over D&D. The idea of rules as physics for example means exactly this. The rules model what happens in the game world.
No, I don't agree. I think it has to give results that are within the plausible range for the genre the game is in and there's no need to show how those results are arrived at. If that means the player or GM describing how something happens, then that's something I'm perfectly happy to do.
Earlier it was mentioned that the multiclassing rules are good simulations. Really? Simulating what? Bob the fighter carves his way through a bunch of orcs, gets the pie and goes back to the Keep. He has killed and looted and done enough stuff that the game judges him to be second level. Upon gaining second level, he takes a level in Wizard/Magic User (take your pick, depending on edition). What happened in the game world? He has done absolutely no training, and has had no contact with any wizards, yet, now he somehow gains the abilities that would normally take years of training to gain. After all, had he started out as a first level wizard, he would have had to spend many years becoming that wizard. But, he spends two weeks killing orcs, and that makes him a magic user? How?
It's probably not so significant a factor with editions other than 3e, since that sort of multi-classing/dual classing is much less common (indeed, it's entirely prohibited in all versions of Basic D&D). I'd certainly never have permitted a character to do that without requiring that the training rules be used, even in a game where I was waiving them for normal levelling up.
Though of course Classes and Levels aren't exactly poster children for simulation of anything in particular, at least when done in the D&D style.