Short answer, No! They certainly look all black, with a tiny bit of white. And black German Shepherds are not uncommon. But Jane and Cash’s puppies are definitely “black and tan”. In German Shepherds, “black and tan” isn’t just what color they are, it is a genetic expression of a color and pattern.
All “black and tan” puppies are born black or almost all black, like Jane’s. Then as the puppies grow up, the “tan”, which may in fact be anywhere to a light cream to rich red-brown, expands and covers the legs, belly, under the tail, up the sides a little, and into the face. “Black and tan” is the traditional coloring seen on most German Shepherds. Adult dogs end up with varying degrees of black on the face, called a “mask”, and on the body, which might be called a “saddle”, a “split saddle”, or a “blanket”. Then there is the “bicolor”, which has the same colors as a “black and tan” but only the legs are tan.
Another genetic color and pattern in German Shepherds is “sable”. Jane’s puppies will not be sable, because both Jane and Cash are “black and tan”. At the risk of getting too complicated, a sable dog can carry the gene for “black and tan”, but a “black and tan” dog cannot carry the sable gene, because “black and tan” is recessive. Sable puppies are born tan, and become more black as they grow up, the opposite of “black and tans”. They end up sometimes looking similar, because they have the same colors, but different patterns, especially as they mature.
There are all kinds of websites about coat color on the internet. These few paragraphs only hit the main ideas which everyone accepts as true. Some more detailed topics are still being researched, and there is some controversy among geneticists and breeders.