Irelia Skin?

Irelia has this one skin that is the Nightblade Irelia. All of her other skins the photo matches what they look like in the game such as the blade's details and clothes. However the Nightblade Irelia she only has the skin's clothes the blade is the same as the normal irelia's blade. The Nightblade Irelia has a black/silver and purple blade in the skin picture however in the game she only as the nightblade irelia clothes she doesnt have the black/silver and purple blade or the blade thing above her head is that a glitch or a minor detail mistake? Btw is this just for this one skin or is this a minor mistake on other champions and their skins too?