You are partly right, but there are also other reasons why the artists don't add alts into the design upon innitial release. :3
It comes back to TJ expressing dislike for having too many dragons in a 'set'. From memory, it's normally been more than four or six, can't remember which.
So as a general rule, most artists who've been around for a while tend to keep their dragon sets between that number.
As you can imagine, in the case of, say, my own dragon? I already had plans for alts but was unable to get them done for reasons on their release date. But that was fine because eventually that was rectified. :3
Needless to say, ideas like this are good because it CAN give the in cave artists ideas. Read though - CAN, not ALWAYS.
Either way, with this idea, if it did go ahead I think it'd only be appropiate on some breeds, and not all of them, anyway, because not all animals have forms of albinoism, and neither would dragons. :3