And in the amount of time(years) you'd take proving it out why not just get some 100% hets from a reputable breeder and have a good shot at homozygous snakes on the first try?

You get what you pay for and again, I'd just consider what you have normals. If, down the line, a random mutation pops up somewhere then more power to you but don't waste time trying for something that likely isn't there(IMO).

Have you ever done business with this guy before? Do you know anyone else who has? Have you fed these snakes yet or seen them shed etc...? I personally would not have bought what you did and kept saving for some with proven genetics.