It’s astonishing. If you google image search “kul tiran flight form color” the variations show up on wowhead along with other sites. I’m pretty sure wowhead gets their data from WoW, so this means the work has already been done on the color variations, yet they aren’t in the actual game.
Just sloppy QA and design to leave these out. It’s like when you come across a chair in the game that you can’t actually interact with to sit in… not really game-breaking, but attention to detail matters in the grand scheme of things.