Don't get me wrong guys. I think it's cool to have some backstory to some of the maps we're playing on, or canon/lore in general like that. But when they have to exclude certain things in the game for the sake of the lore, it seems like too much.
I assume you're talking about playable Elites. They were not excluded because of lore reasons. They were excluded for some other reason and their absence from multiplayer in a story point of view was excused with a story answer of the simulations being only Spartans training with other Spartans.
There was no meeting at 343 where everyone was super ready and raring to include playable Elites when someone burst in and put a stop to the whole thing simply because it didn't fit with the story.
If that was the case, we wouldn't have pizza and fries on our guns, toy company guns, race car warthogs, and Clippy on our Spartan emblems. 343's little meme REQs are proof that story doesn't factor into what does or does not make it into multiplayer, if nothing else is proof enough. We have plenty of stuff going into the game which doesn't jive with the canon of multiplayer.
I see no evidence that multiplayer being included in the story has had the slightest bit of influence on its gameplay or features, even with story being used as an excuse for something which wasn't going to be in the game anyway.