Not sure about your vet’s system, but it could mean that blacking out the mix, means they look purebred. There's no way to know for sure without a DNA test, but I wanted to tell you that Joey's head became white/silver until around 11 months, when it became beige overnight. When he had white hair with black tips, he looked baldish, as if the white hair was scalp, and this wasn’t a good look.
This is around 12 weeks
It looks baldish, but there was hair there, his kerchief was a little big!
He has no more white!