I think the iOS 6 screenshots are just quickly taken from the author's real phone, while the iOS 7 shots are from Apple's iOS 7 marketing. So it's unsurprising,

I think the iOS 6 screenshots are just quickly taken from the author's real phone, while the iOS 7 shots are from Apple's iOS 7 marketing. So it's unsurprising, but not intentional, that the iOS 7 screenshots look more carefully designed to please than the iOS 6 ones.