I'd have to think they know about it, it's discussed in all paint circles I've been in, and was the reason the Tovero mare I was riding was bred to a Tobiano. I don't think the 'test' was available then. You didn't see the Lethal White negative advertisements on stallions that you see now. It was all much more mysterious.
Well, I should clarify. I'm being very charitable calling the people I'm thinking of "breeders". They're mostly just wannabees.
But even so, something like this, I'd have thought I'd have heard about it. Maybe I have and just didn't pay attention because I'm not that fond of paints, or maybe I thought they were just speaking about albino's.
Probably just me.
Becky