Maybe if you see the words written by Mike Mearls you can understand the truth.
Bolding: Because of the staggered release schedule there have been some concerns over both home and organized play, and whether or not people will have enough material to start playing their weekly campaign right off in the new edition and carry them all the way through release. What would you say to people concerned about that?
Mearls: I would say that's definitely where Basic D&D comes in. When the Starter Set launches it's going to cover character creation. Once the Player's Handbook launches we'll update it. [Basic D&D] is going to be a updated a few times when it first launches. With basic D&D you'll have the core monsters, magic items, all the rules for creating adventures, for Dungeon Master guidelines, for balancing encounters, for treasure, treasure tables, encounter tables. This is literally the process I used to outline it: I took the old basic set from 1981 and just the rules in there, the magic items, if it's in there it's in the basic set - except a few things that people don't see as iconic anymore. For monsters, we just went through and said "What are the typical fantasy monsters like Orc, or Ogre?" with a few adjustments for power level in there so there's a nice curve. In theory, with basic D&D, you could run an entire campaign. The core rulebooks could be expansions to that. The core rulebooks are like Advanced D&D.
So if Mearls is calling them the core rulebooks, why when I do it does it ruffle so many peoples jimmies?