Blue Qiraji War Tank

okay soo i saw a guy riding this in stormwind... HOW?

This (and I assume the Red and Black variants) come from the Call of the Scarab micro-holiday event. I have only seen the Blue one in-game. Though you can get the mount from a vendor in Silithus, and mount it during the holiday, it does not appear to be actually learnable, and does not get added to your mount collection. Similar to the Broom which is only available / usable during Hallow's End. These are an updated representation of the Qiraji Battle Tanks, found in AQ

This mount is listed on my Uncollected Page on my Armory.... So the wow page considers it "in the game" but no one knows what from? Or is this just one of those placeholder deals?

https://worldofwarcraft.com/en-us/character/argent-dawn/purgwolf/collections/mounts?uncollected