Then, by that formula, you must consider LDS as part of that One Church, and I know you don't.
There may be some LDS who fit into that cateogory, just as there are some Methodists and Presbyterians and Orthodox who would fit into that category; not by virtue of their membership in any organization run by men, but by virtue of Christ's having written their names in the Book of Life.
The LDS Church is not a true Church as they do not believe in the Christ revealed in Scripture. Nevertheless if God can make Sons of Abraham from stones, then he can make Children of God from Mormons.
When his disciples heard it, they were exceedingly amazed, saying, Who then can be saved? But Jesus beheld them, and said unto them, With men this is impossible; but with God all things are possible.
(Matthew 19:25-26 KJV)
Of course that would include Mormons who have Christ as their Lord and Savior. And Arians. And even JWs.
It would not include those who do NOT HAVE Jesus as their Lord and Savior, whether Methodist, Catholic, Presbyterian,....etc.
Jesus is not in a box or a bottle. He’s revealed in the true scriptures.
Let us imagine that much written about desert island with a shipwrecked non-Christian stranded on it.
A bottle floats ashore and inside it is Chapter 3 of the Gospel of John....no more and no less.
Could the stranded man hear only the Apostle John’s Chapter 3 account about Jesus and become a true Christian? After all, “faith comes by hearing and hearing by the Word of God.”