Bug with Double Youmuu's

I had a Graves in TFT, Intended to give him Youmuu's to make him an assassin. In next Carousel i got another graves that had spatula and they combined into a 2 star Graves. I tried to then place a BF Sword on him in order to give me the extra Youmuu's as with other background changing items it will give it back to you if the champ is already that racial (Except for the bug on Glacials and Frozen Mallet). I instead ended up with a Graves with 2 Youmuu's. Is this an intended efect? Should the game not register the added background and give the item back as it should for other assasains that get youmuu's?