Yep! But in terms of physical size, it wins easily. On a Hasselbad (6x6) the diagonal field of view is about 2.7 degrees. That's roughly equivalent to a 900mm on a 35mm camera. Still not too bad in terms of magnification.
I think thats the point where things just get silly. Was it really necessary to make it that wide? There are 400mm f/2.8s around that aren't that wide, to me that lens looks terrible. Now the sigmonster on the other hand is a beauty. It actually looks like a telephoto camera lens.