Actually, the complaint is that, if the AF you want is in Aurum Vale, you NEED to have completed far enough Darkhold to get another AF anyway.

So a first-time player, like it was my case actually, you have to do two AFs worth of work, because, for example my case, the Dragoon dungeon piece is in Aurum Vale, and the effort nescessary to open up Aurum Vale is the same effort nescessary to get, say, the White Mage piece in Darkhold.

So in case I had both my WHM and DRG quests lined up, i'd need to first get my White Mage AF and THEN get my Dragoon AF. Whereas the AFs that aren't in Aurum Vale do not have the 'virtual' pre-requisite of having a completely unrelated piece acquired.