Like I said, it is a hunch yo.How do we know he's not in the main game...? Seriously, it was first shown for Vergil's Downfall, but that doesn't mean it isn't featured in the main game somewhere. Don't jump to conclusions, yo.
Old Vergil to giant demon spawn: "This enemy appears to be one for the ages. A battle between the great son of Sparda, and one of the most terrrifying beast ever to be seen."
New Vergil against giant demon spawn: "Oh. It's you again. Let's make this quick."
I loved your signature!!! You really did it, after my post.