I agree that you do not need a bonded bullet for a elk but they are nice. Most of the elk that I have killed have been shot with Sierra boat tails and there have been quite a few. But I have switched over to Barnes just because I like the way that they perform. They are not needed but I just like them.
The big thing that you need to stay away from on a bullet for an elk are the type that are designed for rapid expansion such as a Nosler Ballistic Tip. They work fine on deer and antelope but leave a lot to be desired for a elk bullet.