Originally Posted by the///Mthree
There is also the difference in structural rigidity(roll cage), different tire sizes (GTS has 255/285), as well as R compounds, The splitter and wing.
I've never heard a definitive answer. Again - it's probably the slightly different chassis/wheelbase and less rear overhang. In high-stress situations everything matters.
There is a longer distance between A pillar and B pillar support in the coupe. The vertical support is more evenly positioned and anchored in the sedan. That should also have some effect.