Also from the pdf: the carbody looks a bit different (longer short hood, perhaps, though that might be an illusion from the camera angle). Since the engine is, I think, physically smaller than a 16-645, the cab could, in principle, be set a bit further back from the front of the unit.
More definitely, the pdf says the "frame" is new and crash-resistant. So perhaps we should interpret it as "new from the trucks up (though not including the trucks themselves)!
Intresting, given all that, that it looks as EMD-ish as it does: no effort at styling changes for "brand identification". Or maybe they thought about that and decided that, given the conservatism of railroad motive power people, having it me as much like an EMD as possible would be good for sales!