Except for "bleedthrough" blacks... Do you think bleedthroughs are actually brindle? Even so, what explains the parents of said dogs *not* showing any brindle (even if the parents aren't black)?
Brindle + aa (recessive black) - dog will be solid black (recessive black does not allow the production of phaeomelanin in the coat)
Apparently, this is a saddle back dog with brindle markings on the legs. I would think a sable GSD would have the brindle on the tan areas (legs) too.... but not sure.
Unsure though about at dogs that have kbr present, how would this be expressed, if at all?
The reason that Labs can have brindles crop up is that Kb can hide Kbr--so you could have generations of KbKbr ancestors with no brindle showing up until bred to another KbKbr and then you get KbrKbr -- brindle puppies. And there is no doubt that the foundation of the breed showed brindles--but it's easy to breed away from a dominant color--you just don't breed to it. So, how would the gene "hide" in generations of non-brindle ancestors?
Black in GSD works the same way, if not worst given as GSDs have two types of black. Labs have one, Kb.
Similarly it is unknown what brindle + agouti/sable makes and/or appears as so it is possible that the darker or more heavily marked sable GSDs are carrying brindle somewhere in their genetics.
Bi-colors and blanket types can likewise hide brindle unless really examined due to the small amount of tan that is actually visible in either coloration - a black & tan would be glaringly brindle.
True black sables are said to be some sort of a co-dominance between aw / sable and a / recessive black.
The website - facebook - claims this to be a DDR black sable.
An animal marked that richly is going to disguise a lot unlike closely examined.
Similarly most show line GSDs are highly and heavily inbred - not to start anything - but I've seen sires on Pedigree that has supposedly sired hundreds of offspring. A high inbreeding cofactor is going to eliminate unusual traits - brindle - in show line dogs as they are bred to fit the standard as close as possible.
Old line patrol dogs / DDR - Czech \ and high level working animals / bloodlines are more than likely to carry unusual traits - brindle - than show animals.