The question is if Sam was produced from a spider X spider breeding. Do you know?

7 for 7 spiders from a heterozygous spider would be a 1 in 128 chance. So it's possible he is only heterozygous and you are just lucky (well, except on the live baby count). But, keep breeding him and let us know, especially if you can confirm he is from spider X spider so even has a chance to be homozygous.

To me, every dominant type mutation has a chance to be homozygous lethal until evidence is presented to prove it's not. I believe woma/pearl fits the definition as the pearls apparently don't survive to breeding. I will not be surprised if there are several others. I don't think it's any less responsible to mention the possibility than to not mention it. One possibly errors on the side of protecting the sellers and the other possibly errors on the side of protecting the buyers.

It's also important to remember what it would mean IF spider is homozygous lethal. It would NOT mean that regular spiders or spider crosses would necessarily be any more likely to not hatch or to die early than any other ball python. It would only mean that homozygous spiders from spider X spider breedings would not survive to breed (perhaps not even hatch).

Because people are long since no longer buying spiders with speculation of producing an awesome super whether or not spider is homozygous lethal (or even dominant vs. co dominant) really doesn't matter much. It’s mainly an academic question that we should probably have an answer to by now. People buy spiders to make spiders and awesome combinations which are proven and if spider is homozygous lethal it will not effect that at all.

By the way, if it where homozygous lethal and the homozygous didn't hatch then spider X spider breedings would produce 66% spiders from 3/4 sized clutches – so the same number as 50% from a full sized spider X normal clutch. The 75% spider ratio from spider X spider assumes that homozygous spiders hatch and look like regular heterozygous spiders.