Yes, those are markers, though not the strongest ones I've ever seen. And as already stated, they don't correlate 100% with the piebald gene... but I've had pet store owners tell me that in recent years a lot of breeders have been unloading het and poss het males as "normals", rather than going through the trouble of trying to sell them as hets. So no guarantees... but it never hurts to dink around.