It could be. I've mostly had good luck with the China boards but certainly you have to expect they don't put the highest priority on quality control and using genuine components. I've never seen an Arduino with the ATmega8U2, though from that Playground page I guess it's a thing. It seems strange that the computer identifies it as AT90USB82, which is a different chip from the ATmega8U2.
It seems that people almost never have success with trying to update the firmware on the ATmegaxxU2 USB chips on the Arduino boards. My instinct would be to use an ISP programmer to upload the firmware instead of messing with this DFU thing but I've never had a problem with any of mine so I've always just left that chip alone.