There's the question why a screencap was taken for a case on a site that has the flowchart Home >> Nintendo Switch Mini >> Accessories >> Protective Case. When Nintendo Switch Mini is already its own category, why not just use that page? A mockup all around.
The website page isn't a mockup, you can go to the site yourself and go to the Switch Mini category. http://www.honsoncn.com/nintendo%20switch%20mini/
But the image itself is likely a mockup. Other images on the same page have a different (much lower quality) image, with a different design.
Though maybe the reason the other one looks so much better is because it's actually the first legit image, unlikely but possible. They're pretty sure it's coming though by the looks of it.