User blog comment:Madman97/The Aedra Vs. The Daedra theory/@comment-3025184-20131010203442/@comment-9062114-20131011034843

People call the Time Over-Soul "Akatosh" so that's why he said it. He was the first Dragon born from the Time Over-Soul. Paarthurnax wouldn't need to explain exactly what Alduin is as it had nothing to do with the quest at hand.