Kia has tried to hard with this one.The rear quarter panel looks like a bolt on after thought, not flush with rear door only made worse if you choose it with a different colour quarter panel to rest of car. Its also expensive for what it is.
It is a bolt on, its part of the aero package to help with range efficency, there is a gap behind it from back windows to rear.
Not seen one yet @Rico but surely that will cause more drag than a relatively flat sided vehicle where air can more freely flow past rather than be restricted. It might help with down force in a similar way to a spoiler but its not exactly a quick car. I also wonder if it will whistle at high speeds LOL.
Like ?I say not seen one in the flesh yet but going by the images and reviews Ive seen my personal opinion is it looks weird, ugly and spoils the look of what could be a good car. But that’s only my opinion