My curiosity piqued concerning the frames of Baldwin switcher offerings, I did a bit of research. It appears that somewhere along the line during the DS series of switchers, the frame corners were revised. SO, it does appear that some of the DS series can be missing the angled frame corners.
One of the fascinating aspects of Baldwin diesels: The company would introduce modifications and revisions to an existing line without the creation of a new designation.
As evidence, here's a builder's photo from Baldwin itself of what is captioned as a DS-4-4-750: