Some of your German breeds will revert back to the original hair coat. It must be a funny gene or something. At least that's what I heard somewhere.
It doesn't seem to affect the prey drive or natural hunting drive.
This guy was a purebred Drathaar that was supposed to have longer hair like a usual Wirehair. Registered with NAVHD and all that. Didn't make him any less of a hunting dog.
(Not the Airedale)