I'm not seeing how this:
turns into this:
The kidney grille openings appears to be taller on the mule than on the render but maybe that's because there aren't any actual grilles in the openings yet.
The large lower intakes also don't appear in the same position on the mule and on the render. On the render, they're further outboard, under the outside head light. On the mule they appear much further inboard and would be right where the vertical body element on the render is, between the inner and outer lower intake openings.
That said, I've seen early mules in person and they sometimes have sheets of plastic literally screwed into the underlying sheet metal with sheet metal screws, to completely hide the underlying shape. Only when the B&W camo wrap is applied to smooth body panels can you have any idea what the actual shapes are.