That does look odd - I'm used to the seam line being horizontal when mounted. Live and learn I suppose. I was rather surpised back in the day when I first learned that some models of drop tanks were made from pressed paper composites. There's always something new to learn.
Modelling is one of those endeavors where historical knowledge weighs in pretty heavy. Unfortunately, that body of knowledge isn't always as full as we need it to be and sometimes the facts get a little polluted. If we don't know how something looked or worked we might adopt the convention that it must have worked roughly the same way as this similar object that we do know a lot about. After all, we know how some organizations strive for standardization. Pretty soon that adopted convention gets canonized thru generations of repetition. That's how seam lines get removed or positioned correctly for one set of circumstances and incorrectly under another on a different type of aircraft or shackle design.
Than somebody digs up a picture that challenges conventional thinking and the headscratching begins in earnest. The guy that was the first to say "Find a detailled picture of the subject you're modelling and you can't go too far wrong" was pretty damn close to the truth of the matter. Which means on that point we're kind of screwed at most turns, given the rather short life span of photography and the places and events a camera lens likely never intruded.
WmB