Since Tom Baker refers to his female as "Special" I'm assuming that she isn't as normal looking as the dilute gene carriers that make platy appear to be. Maybe she is on the subtle side compared to mojave or lesser or maybe even phantom but still I'm thinking a visible morph. As a visible morph, I would not be surprised if it makes a different looking pastel. I don't think that necessarily means the special gene isn't another allele in this group. Of course it could go either way but I'm also expecting it to be another allele and the crystal to be one of the more colorful supers in this group. I'm not sure "leucistic" is really the best name but I think everything from the homozygous lesser to the platy to the crystal to the super phantom are all alike in that they all have two mutant copies of this gene and the differences are which mutant versions are present. I think the ingredients lesser, butter, mojave, phantom, Vin Russo, mocha, dilute/hidden, special and probably a few more (Marshall VT near me proved another this year) are all the same gene, just distinctly different mutations of that gene. So I would consider the platy and the crystal to also be supers of sorts with no room for a normal version of the gene just like the super phantom or the super lesser.

Now the relationship to piebald was unexpected but different in that it appears that an animal can be both homozygous piebald and lesser so not alleles. Maybe lesser just lets the piebald white spread further. Sort of an interaction like pastel and cinnamon to produce an unexpected combo but still separate genes.