That’s because that is an accurate and official teaching of the LDS Church, that Christ would return to the Mt. of Olives. The other is an additional appearance, since he is the Creator and Savior of all the earth, not just one location.
Here’s the official teaching.
http://scriptures.lds.org/gs/s/35
NIV Rev 18-21
18I warn everyone who hears the words of the prophecy of this book: If anyone adds anything to them, God will add to him the plagues described in this book. 19And if anyone takes words away from this book of prophecy, God will take away from him his share in the tree of life and in the holy city, which are described in this book.
20He who testifies to these things says, “Yes, I am coming soon.”
Amen. Come, Lord Jesus.
21The grace of the Lord Jesus be with God’s people. Amen.