Why has St. John or the three Nephites not come out in support of the LDS Church?

From the official [LDS website](https://www.churchofjesuschrist.org/study/new-era/2017/11/to-the-point/are-john-the-beloved-and-the-three-nephites-actually-still-on-the-earth-if-so-what-are-they-doing?lang=eng) : > Yes, the Savior granted to John the Beloved and the Three Nephites their desire to tarry on the earth. What they’re doing is bringing souls unto the Lord until He comes again (see D&C 7:2; 3 Nephi 28:9). Now I must say, this is the most curious doctrine. I have never heard of it before, and it seems quite absurd. So I have a question. If St. John along with the three Nephites believe fully in the truth of the LDS faith, why have none of them come out in support of the LDS church? Surely this would be undeniable proof of the truth of the LDS faith?