“Ever find it odd that...”
No. God kept secrets from Moses that He did tell to Paul. His timing, His choosing. They all jibe with God’s promise to Abraham—“In you shall all the nations be blessed”—and find their ultimate fulfillment here:
“Therefore remember that at one time you Gentiles in the flesh, called “the uncircumcision” by what is called the circumcision, which is made in the flesh by hands— remember that you were at that time separated from Christ, alienated from the commonwealth of Israel and strangers to the covenants of promise, having no hope and without God in the world. BUT NOW in Christ Jesus you who once were far off have been brought near by the blood of Christ. For HE HIMSELF is our peace, who has made us both one and has broken down in his flesh the dividing wall of hostility by abolishing the law of commandments expressed in ordinances, that he might create in himself ONE NEW MAN in place of the two, so making peace, and might RECONCILE US BOTH to God in one body through the cross, thereby killing the hostility.”—Ephesians 2
God did not reveal this to Moses, and Paul would have been STONED if he had preached this in Moses’ day. Remember, God “knows the end from the beginning” and, being outside space-time, He spoke of the coming of His Son and only revealed Him “in the fullness of time”.
The same with this “mystery”, the fulfillment of His promise to Abraham. His secret, His timing.
Can I ask you a question? With millions of Mormons in the world, why don’t you believe Joseph Smith?