Where does 343(Frank) say BR is unlockable...???

I keep hearing people say “We need to unlock the BR for loadouts/w/e”. Or other weapons as well.

Well I did check out the sparkcast thing. Didn’t remember hearing them mention that.

So where did this come from? Is it like a true fact, Is it written down, Because I sure don’t remember hearing it there. Or anywhere else (Except here)

So link me to where it says this.