Not Similar
This is not similar to clownfish. These tangs are naturally occuring in the wild. Completely white clownfish will most likely not survive in the wild, because they feature too much of one color and dont blend in well.
Directly from ORA they acheive there fish through selective breeding. No one is making Koi Tangs, but someone is ORA is pairing up fish that have a genetic defect to get more with that defect. Which is why i think inbreeding is very prevelant in ORA's fish. That is why ORA has soo many fashonable fish, stubby heads, slack jaws, misbars, picasso, snowflakes and their newest abnormality platnium clowns.
Clownfish have these patterns for a reason, evolution/survival of the fittest. The patterns on clownfish correspond to the anemones they host in their ability to blend in.
If one pair produces two all white fish, they are selected (Selective Breeding) from the broodstock and paired up so they can produce offspring that are more then likely going to white.
Just like LE corals if people keep paying money they will keep producing these fish. Its basically a degredation of the gene pool. That is why ORA constant has new breeding pairs.