Fenders are always thin, they should be, the offer no structure really, and should be easily deformed on impact. Some are made of plastic.
What Jason is talking about is the inner structure that many Chinese cars, even Chinadubs, are made from. The Chinese do not value life like we do, so their safety standards are pretty lax. They often use lower grades of steel, and they soldier on reskinning old designs from the '80s... only in some cases they somehow manage to make them worse. There are some pretty dramatic crash test videos out there of some of these cars. Seriously awful. A 1985 German or American built A2 Jetta or Golf actually holds up BETTER in a crash than a 2005 Chinese Jetta that is a facelifted version of the same car.
Given how horrible the fit and durability is of so many Chinese made replacement car parts, as well as pretty much any tool, appliance, etc. that you may buy, despite on its surface looking and feeling just as good as the original, I'd say the idea of a Chinese car in total, even a Volkswagen, is not likely to be as good as we'd think it to be. At least, not by our standards.
But their prices reflect that. Better steel may add several hundred dollars to the price of a car, and more inner structure steel means more steps to assemble it, and more energy to weld it. They leave that stuff out.