That's an interesting point. I read a book on pattern drafting from the 1940's that had pictures of the ideal posture and an over-erect posture. What was surprising to me was that the over-erect posture was what I would consider the posture of someone standing up straight. I've only made one dress from a genuine vintage pattern, and I found that if I stood up straight, the back was too long, while standing with my shoulders in what feels like a more natural position make it fit better. I've found the same to be true with the Vintage Vogue patterns I've used, but I don't know what, if any, modifications have been made to those patterns.