Here's my guess on why one is up and one is down. We have projector headlights which basically means the instead of the light being spread evenly there is a point where the project cuts it off. This is so when you have your low beams on the light gets cut off before it would be shining in the eyes of oncoming traffic and is only displayed on "the bottom half". For high beams they opposite is true. You want the light to shine on the "top half" so that you can see further down the road.

My guess is that both projectors for high and low are the exact same part and one is just installed upside down from the other to cut manufacturing costs.