I have a few thoughts on the subject.
For one, it's not unusual for game companies to literally have no idea what is going on with their projects. "Easter Eggs" originally started out as things coders and artists put into the game without telling the development team or publisher. I've long taken the approach that if something, even if irreverant or a nod to another game, winds up getting mentioned in the cluebooks or whatever then it's not a real easter egg. REAL Easter eggs have included things like additional audio files with messages from the creator, or game characters saying creepy/out of character things (or their voice actor in the character voice more specifically), extra graphics files, or even text messages hidden in the game code itself if you go in with programs like the ancient "D-Sector".
Of course you don't see this as often because of the possibility of being sued, and of course the reaction it might get from some people. One famous example of an "easter egg" in a game was a gay mission/kiss (guy on guy) for the game "Simcopter" which caused quite a stir at the time, being roughly the equivilent of the penis in the back of the Disney "Little Mermaid" artwork.
The point is that the DLC might have been put into the game without EA as a whole knowing about it, with the coders who did it fully knowing people would find and unlock it. This could have been done for a lot of reasons, such as it being easy to do and the artists wanting their work to be seen by PC users, to a protest against the way companies are doing DLC in games. Which brings me to the second thing I wanted to say:
This right here is an example of why I think things like paid DLC and cash shops are out of control. The very existance of "already on the disc DLC" shows that the attitude isn't one where the company is developing DLC to extend the playtime of games, but rather finding things they can hold back/cut out/whatever and sell seperatly for money. Even with extra weapons packs and the like, I find it quite annoying when they are already on the disc and your basically paying for something that you already bought.
I'll also say that I'd imagine this annoys some artists as well, some guy sits down and designs all these armor and weapon models, and wants them to be seen, and then the developer says "well, we're going to lock the stuff you did out of the game unless someone pays $5 a pop to see it", which of course means that a good portion of the player base probably isn't going to experience what you made, when you thought it was going to be a main part of the game. Irritation like that, especially if it was going to be omitted from an entire platform, could lead to relatively minor acts of rebellion... and that could be what we're seeing here.
That's just my thoughts on the matter, I very much doubt EA would go through all the trouble of lying about this. What's more they seem pretty stupid because even if they hadn't intended it, this would have been the point where a company that greedy and two brain cells to rub together would have screamed "piracy, get out of our code hackers" and then immediatly put up DLC unlock packs for whatever price.
I mean I'm glad they haven't done that on a lot of levels actually, but it would have been more of a common sense reaction than the current "we deny it despite it being right in front of us" and making it clear that they really have no idea what's going on with their team. Except in extreme cases, companies tend to wisely keep their mouthes shut about real easter eggs in their products.