So, since John 3:16 is not a false gospel, then Jesus saves those who believe in Him through that word (and others).
Whether they’re Swahili, Arab, Zarathrustrian, Islamic, Rostafarian, Mormon, Baptist, etc. when they believe in the gospel.
And then God finishes the work. That’s what I believe.
God never saves with a false gospel. And half a gospel is no gospel at all. I know for sure the LDS do not have a saving gospel and it’s wrong to let them believe they do. In Acts 20 Paul said he was innocent of the blood of all men for he had not failed to declare the whole counsel of God. When we affirm a false gospel we help to condemn men and cannot say we are innocent of their blood.