The GWP originated from Drahthaars imported to the US. I’m sure there has been some crossbreeding of Pointers into the GWP breed.
The Drahthaar must pass a very rigorous testing and evaluation process in order to get a breeding number. Only puppies from two certified breeding dogs can be registered as Drahthaars. The standards for a registered GWP pale in comparison. Any uncertified Draht can be registered as a GWP and used for breeding.
Breeding Drahthaars must pass evaluation for form, coat, bite, and have x rays for hips and elbows. Dogs that pass the final utility test (VGP) must have a high degree of mental stability, cooperation, and drive.
It’s not a fool proof system, but it’s a very good one. The odds of genetic outliers are greatly reduced. The same cannot be said for the GWP gene pool.