I sorta read that as them just not wanting to take the time to put it in Limbus. Seemed like they had the whole thing set up for Ultima and Omega, then people started requesting AF+2. Since they didn't want to put the whole thing on hold for a couple months to add and balance a drop system and the stats for AF+2 itself, I'm guessing they just fed us this side note and merrily went about their business.

Or hey, maybe they've always had plans for AF+2 in SoA and just didn't want to leak that info too soon.