Yup, I was just about to say the same thing. It's also referred to as split leather or bicast/bycast leather. So the backing is leather, and it has a layer of polyurethane applied to the surface, which is then embossed with a leather pattern. It's typically used on shoes and purses to give them a glossy look.
But I can tell you that this cover is far from glossy. It has the exact same surface feel and sheen as my official K4 cover. I just handed this cover to my husband to examine, and he believes it's real leather.
Also, I noticed the center part (the hinge) isn't glued to anything (for flexibility), so I was able to examine the side of it, like a cross-section. And I just happen to have a piece of genuine leather that I purchased for a craft project. I compared them both and the piece on the cover looks just like the genuine piece. And looking at the edge (cross-section) I definitely don't see any polyurethane layer.
So I'm pretty sure this thing is real leather. But I'm really interested to hear what everyone else thinks when they get theirs.