They have that type of conformation in order to have a type of “spring” to them, from what I understand. I bet your GSD is beautiful, I would love to see him if you have a picture.
I would love to post his pick but am not smart enough to post pics on FR...lol
I would worry about hip dysplasia with hips manipulated like that. Your dog is beautiful too and big. He is 50 lbs bigger
than mine and mine is big.