Rudolf, I understand the reasoning behind the definition of leucochilum, where the delineation from gofefroyae is a spotless pouch.
However as far as I know, the dark black 'leucochilums' come from direct pure white pouched leucochilums. As a result of this heritage, the names were maintained to reflect this lineage.
Since leucochilum is a 'distinct' species from godefroyae based on current taxonomy and Kew checklist, the name has been maintained in this line breeding, eventhough it obviously does not fit the initial original description of this species.
It is my thinking that this definition must be revisited by today's taxonomists to broaden it to reflect current breeding. One cannot simply renamed a leucochilum line into another species by virtue of these selectively bred traits.
For the record, I myself think they are the same species with varying amounts of color in their pouches. You see, not all pure white pouched leucochilums breed 100% pure white pouches. Nor do all godefeoyaes never produce pure white pouched offspring.
Therein lies the dilemma that will forever be a moot point in these kinds of discussions, until a taxonomic review clears these distinctions between these two species.