There is a difference between Leucistic and Leucophore. Just because an animal exhibits an abundance of leucophores dose not make it leucistic.
Leucistic- All pigment except that of xanthophores if absent, producing an all-yellow appearance (Mattison, 1986). White, colorless, albinistic (Peters, 1964). Appearing as white (Barker, 2006). Absence of pigment (melanophores and xanthophores) through out the body with the exception if the animals iris; usually a solid white animal with black or blue eyes.
Leucophore- A white chromatophore (Holmes, 1979). One of two types of guanophores characterized by the presence of guanine in the form of granules (Peters, 1964). In general, leucophores and iridophores are both considered guanophores, but these two chromatophores should be distinguished because leucophores contain white granules laden with uric acid, whereas iridophores contain reflective platelets (Hama, 1975).
What needs to be identified is are the mutations exhibiting an abundance of leucophores allelicly joined. It also needs to be understood that all of the information available to day in reference to ball python mutations is strictly phenotypic. There is no biochemical or DNA research done to date on ball python mutations. In fact we do not even know which chromatophores exist in ball pythons and in what layers of the tissue they exist. There are a number of theories that cannot be confirmed or denied simply by phenotype.
Can they really get any whiter than this?

Greg
Graziani Reptiles