I quoted you the official stance by your Utah government. That's the law. The HOV lane is NOT a passing lane. Period. There is no duty, by law, to move over to let anybody pass you.
It may seem weird to you, but the passing lane is actually to the right of the HOV lane. That is the designated passing lane in Utah whenever there is an HOV lane. By law, if you'd like to pass somebody in the HOV lane, it is up to you to move into the passing lane to do it.
That is how Utah law is written.
Now, everyone is free to a contrary opinion, but opinions do not change the way the law is written.