I have no idea why someone would come to the conclusion that monolithic's are less likely to expand at a guns peak velocity.

Now if one wants to argue less penetration due to over expansion I would consider that since it doesn't defy the laws of physics. Even then that's depends on the integrity of any bullet at high velocity impact.

You just do the best you can and use a bullet that stacks the odds in your favor given the most likely scenarios. For elk, that's a bullet on the tougher side of the bell curve.

Even for sheep, a lot of guys like the more assured penetration of monometals just in case they hit bone such as the shoulder blade. Especially in the open country of the north, where a sheep going a ways before succumbing is not an issue. I actually used a TSX on my Yukon sheep hunt - not for the sheep but because I also had a grizzly tag. The country was wide open above timberline so I was comfortable with my choice and it was not a problem anyway (ram spun around and fell dead at the shot).

Despite that result, if I were lucky enough to hunt sheep in more treed/brushy country, I would not use a monometal but instead use an AB, partition, or even plain old cup and core bullet.

You may got to YouTube and watch bryan litz video. Pitch, yaw, and bullet path. I believe your talking about being able to shoot smaller groups at longer range. He did have a thread at long range hunting testing this.