I believe several years ago the former Morph King Reptiles bred lesser + mojave males to a large number of normal females (15?) and also produced about 50/50 of mojave and lesser with no normals or leucistics.

This is what concreted the allele idea that had been floating around for a few years before that. As stated in a post above, it looks like within this complex these are all DIFFERENT mutations of the SAME gene. Rather than there only being two versions of this gene like say spider and normal for spider in the case of that gene it looks like the blue eyed leucistic complex has many non normal versions of a single gene. So the lesser + mojave leucistic has it's two copies of the bel gene taken by those two different mutant versions and has no room for a normal version of that gene. When a breeding occurs each parent can only pass one copy of each gene so with lesser and mojave being two different versions of the same gene the combo leucistic can only pass one or the other on but not both.

The difference with say a bumblebee is that spider and pastel are different mutations of DIFFERENT genes so can be passed on in any combination but the rules change with alleles and there are enough examples now with the blue eyed complex, the super stripe complex, and perhaps even a black eyed leucistic complex that we need to understand how they work.