We have an 2011 SX White Koup and we don't have those creases...for now, hopefully it will not show up next winter !!
But you know what, we also have an 2009 Black Rondo, second winter with it and BANG ! a crease appear on the both backside panels, more visible on the left one and for sure, the superdealership we have here says "it's normal !! there is a reenforcement metal plate inside...bla bla bla...a kind of bullshit. They just don't want to assume it's a real paint problem and spent money on it.
By chance, I really like drive those Kia but they will lost some sell if the dealership don't give a better service.