Yes, interestingly this conversation came up off the forum and was almost spot on with what you're saying, Hunter. I suggested that I really liked the wider chest I'm seeing on a lot of Mals, and that I thought that generally the GSD is suffering from a narrow chest. It was pointed out to me that a wide chest does not necessarily equate to athleticism, and that narrow chested breeds often tend to be more athletic than GSDs.
I think one must be REALLY careful when talking about conformation in saying that any one thing is "the reason" that a dog can turn. I'm sure the whole packaged is involved (thus my comment on croup angle- which I swear I've read on this forum that croup angle is hugely important for collected turning). But again, I'd like to first understand if the width of the chest serves any particular function for the athleticism of the dog.
C-ATCH Pimg - DOB: 2/06, UJJ (x2), DJ, HIT, CA, CGC, High in Games, Reserve High in Standard- CPE Nationals 2014
High Jinks vom Neuanfang RATO, CA - DOB 9/12 (Gotchya Day: 1/23/2013) agility superstar in training