Interesting. According to
Wikipedia, PU leather, also known as bicast or bycast leather, is actual leather with a layer of polyurethane on the surface (presumably what the "PU" stands for.) It seems that although it contains actual leather, the leather is responsible for pretty much none of the properties of PU leather.
It doesn't seem all that surprising that a $10.99 Kindle case is made of rather inexpensive material.