Exploited Cus, uber rich folks bought them from the exploiters a few years ago, hid them in their stables, and now may have resold them to unsuspecting re-subscribers (since they know that these are to be deleted on sight), likely for mint gold. These pets have escaped the "fixes" somehow, to the pet revamp corrections of bugs and exploits.
Very rare to see nowdays, but seen publically displayed from time to time at the pet training locations. When I see them at the training locations, I keep quiet of the event, in the fear that a new wave of pet revert or "fix" may happen and hurt thousands of players and all pets, like it did a few years ago.
But yes, it is an insult to the honest players that play by the rules, and spend many hours in the taming profession.