I believe SoFIA 3G is actually based on XMM 6360, while SoFIA LTE is cut-down 7260.
That said, the size differential between SoFIA 3G and LTE can be explained by moving from ImgTec G6100 -> G6200, +2 cores, and LTE.
It's the comp to Merrifield (bigger than either of these) and Bay Trail that has me intrigued. That being said, Merrifield was mostly GPU, so I guess if you cut the GPU size in half, optimize the cores for lower frequency operation, and put connectivity into the RF chip (and not the actual SoC), then I guess it's explained.