You've found one of my great conundrums. They call this fault "snowball", where the color is only on the tip of the fiber. I've read that in one version, when the snowball coat molts out, the new coat will come in normally, and never be snowball again. Let us know if that happens, I'd be interested to see. Reason? So far as I can tell, no one has a clue what causes snowball in the junior coat.
I have a snowball problem in some of my angoras, but it's a genetic fault that transmits to the kits. I've spent a number of years working on the texture of the coats, so they are soft, not hairy, but don't need much in the way of grooming. That and gentle personality have been my main requirements when choosing the next generation of brood stock. Now, I'm trying to weed out the snowball problem, but it's tough because I haven't yet found the genetic reason for this fault.
There is the steel gene that pushes the middle fawn band up to the tip, causing the gold or silver tips, but that isn't this, because the outer color is still the correct outer color, and then everything else is white. Dominant black pushes the outer dark color all the way down into the fiber, that sure isn't snowball. Non-extension (fawn) pushes off the dark section, leaving the fawn band on the tips and no dark undercolor. Wide band makes that fawn band twice as wide. Could there be some variation that carries wide band, but leaves the dark color on the tips? Just a theory.