Nooo... he's not actually wearing really old-fashioned clothing; pre-Goryeo clothing looked a little like a shirt/robe over pants (the robe opens completely like a haori or kimono). I thiiiink that kind of collar is post-left-right-switch, particularly because it's got the white lining sewn on. Aiiiee! Now I wish I had stolen that Korean costuming book from the library ;).