Sigma seems to have an "enhanced" double gauss design, by the way:
Very true, I would say. It's very similar to, but simpler than the 35mm, and it looks almost like they took a double gauss design and added an entire set of front elements to correct all sorts of aberrations, almost like two lenses in one. Here are the two designs compared to the double Gauss of the 1.2L (bottom):
(Top to bottom: Sigma 50mm A, 35mm A, 50L 1.2)
Note: that 35mm A has some engineering gone into it; makes the 1.2L look shamefully simple (and overpriced despite the elements being bigger of course!!!).