Gangplank conqueror keystone bug

Does the new keystone Conqueror work on Gangplank's Q? From what i read from the description it sounds alot like Grasp of Undying keystone that Gangplank can abuse with his Q. However upon testing it out, it doesn't quite apply it. Does the difference between next auto attack vs first auto attack make a difference in how the ability works. Sorry not sure if intentionally created to not work or if it is a legit bug.