It's believed that mojave and special are alleles, two different versions of the same gene (other versions of that gene include lesser, hidden, mocha, and Vin Russo). Each animal can only have two copies of the same gene regardless of how many different versions of that gene exist in the population. That's because each parent only gives one copy of a given gene. A super mojave would have no room for any other versions of this gene including the normal version of the gene or the special version. The reason you can get a double homozygous cinnamon and pastel is because those are mutations of two different genes so an egg can get both mutations from each parent.