The answer we've gotten so far from ZOS explaining the 50+(+) zones is that we will be, "seeing through the enemies eyes," when experiencing those zones. We know that we will be doing the exact same quests that those zones give to their respective factions, they are just boosted up to a higher difficulty. So, I'm looking forward to seeing how they explain it, but I'm not too worried and think they will do well enough to do so. I doubt it would be a fairly ridiculous explanation.