Marketing guy, looking over engineers shoulder: "Can you make the seat tube... like swoopy?"
Engineer: "Like this? That just adds weight and reduces the structural integrity of the frame."
Marketing guy: "Perfect! Send it to manufacturing!"
That bike is at least 4-5+ years old. It went through a few minor changes but yeah, that's it. I rode one while I was in Japan quite a few years ago. At the time, that was about as nimble as you could get for DS riding and whatnot.
This was before the Evil Imperial. But, the wacked out seat tube angle is the same concept. Lower it to get it out of the way up front, raise it to have a more "normal" seat position....