Yuck!
Good question. This postion was hammered into my skull as a junior. In fact, I was shown the b&w pic that the drawing was based on again and again. Yet I have seldom seen the best do this and in fact I do not think Hogan did it. Seems like a recipe for swiping it to the inside and getting super-duper underplane. Ball doesn't care, right? I think Carl Lohren was adamant about this postion, as in VERBOTEN! I think he advocated a right arms that was relatively straight and shoulders that were open to the target line. The more I pour over old instruction books the more I find references to a simplistic understanding of "d-plane" in the sense that a certain degree of "swinging left" is required. I recently saw that in the Toski/Flick/Kostis tome. Toski even mention that if took notice of a par-3 tee box at a tour event the divots trend left! I think Lohren's adherence to an "open" set-up is the same kind of deal.