i was checking for a normal Black Classic flap with GHW few months back and a reseller called that a unicorn and decided to charge 1000$ more than retail so i think to Resellers everything is a unicorn but i think true unicorn are rarest materials/rare colors or Hardware finishes ..
Like the Himalayan Birkin
Himalaya has been spotted at a number of resellers too. It seems to be more common than before?