Please correct me if I'm misunderstanding the question but here is a theory on how those three RDR leucistics where produced:
Maybe lesser platinum and phantom are either completely the same (with differences in appearance being due to other genes in the two lines) or two different mutations of the same gene (alleles). Either way the leucistic is homozygous for mutant for that gene (i.e. no normal copies of that gene). It is either homozygous for a single lesser/phantom mutant gene or it has one distinctly phantom copy of that gene and one distinctly lesser copy with no room for a normal copy (I'm not sure what the technical term is for this).
In corn snakes a similar thing happened with motley and stripe. At this point they are so mixed up with such a continuum between the original motley and the original stripe that it's hard to separate the two once distinct mutations. However, initial breeding results showed that they are on the same gene, i.e. homozygous stripe to homozygous motley produce no normal double hets as expected if they where two different genes. This is because neither parent had a normal copy of that gene to give the babies. They ended up looking somewhat in between stripe and motley but it’s hard to predict what the two mutant allele offspring will look like. I suppose if they where two very different mutations of the same gene it might even be possible that they would look normal but when bred together would never be able to produce anything less than other double hets.
I'm still unsure as to how one would prove different mutations of the same gene vs. the exact same mutation. The idea of interference between two different mutations of different genes can eventually be disproved if the leucistics created from the original cross always breed true with each other (indicating they have no normal copies of a common gene between the two original types). Also, if it does turn out that super lesser, super phantom, and super mojave all look the same then the next test would be to breed them together and see if as expected they produce no normals and only leucistics.
This is all just a theory and it's particularly a stretch including mojave in this discussion just because it looks a lot like the other two which are the only ones crossed so far.