Agree. I guess I was implicitly saying, I didn't see any reason other than marketing. I suspect they were looking for ways to add value to the LE, and given the emphasis on digital content, it sounds like something that would have emerged from marketing discussions. As you said, if it were a balance thing, 343 would have not granted early access to so many and created a schism in the player base purely for marketing purposes.
I wish I had more confidence in that last sentence than I do.
It seems to me that if 343 wanted to meter or throttle player progression so a relative handful of players didn't blast through and get the specializations early, the way to do that is by limiting XP accumulation. And there we again have mixed messages: Double XP Dew! Also, daily XP cap.
Sort of like, only two specializations unlocked at launch! Unless you buy the game early (in the US) or the LE.
It's a needlessly convoluted and self-conflicting setup. The game and community has not been well served by it.