User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-67.187.118.44-20150615164326/@comment-3045936-20150615200005

We don't know why he left them out. Maybe as they might not have been, participants in the war he didn't bother saying them. All we know is this '' Long before God made Angel and Man, he made the first beast." Despite each Archangel basically having the power individually equal to an army of Angels, they are still Angels first. So why state them, separately in everything? I believe Death just stated the participants in the War against the Darkness.

Or they changed it.

Or a script error or canon oversight.

We don't know, and Death's statement from season 7 is more informative than his season 10 one. As season ten he quote was about the darkness itself, and the war against.