He's probably talking about the health problems associated with white in several breeds like hearing problems. He is right that they are cream and not white like those that do suffer from these problems, but that isn't related to the general health problems white GSD's suffer from due to a restricted gene pool. This happens in other breeds too where breeding for a non standard colour (or even a popular standard colour) and is purely due to the fact that there are a large number of byb and puppy farms breeding these dogs without any care about health and temperament. You can see similar in chocolate labradors due to their popularity, although the balance is being redressed as more good breeders are breeding chocolate.