To believe you can get a homozygous spider from a spider X spider pairing you have to assume:

A) It's a grand conspiracy by a handful of ball python breeders to deny the existence of their homozygous spiders.

or

B) None have ever been produced from any of the spider x spider pairings (just a matter of bad luck)

or

C) There are homozygous spiders that were produced but have never been bred so no one knows they are homozygous spiders.