Draenor Bonus Objectives over level 40

Hey all! I’m working through my first real character experience and I was hoping someone could help me out. I’m doing Loremaster and I’ve wanted to play with friends that are level 60 currently. I’ve heard that you can out level the bonus objective achievements for Warlords of Draenor at 40. Can someone confirm or deny that this is a thing, or are they unlocked if you go over them at a higher level.