Good question! (Ignore my previous answer... LOL)
I always thought the white German Shepherds didn't look like GSDs in structure, unless you had one born of two coloured parents with correct conformation. It is indeed true that there are white dogs amongst the oldest shepherd dogs (among other colours such as brindle) - Greif von Sparwasser was white!
SG S-Hunter vom Geistwasser CA CGN TT (Airport Wildlife Control K9)
Zenna vom Geistwasser
"May my enemies live long so they can see me progress."