to all here on this thread,
As I read the Bible, a LOT of protestants and a LOT of Catholics are going to be surprised at heavens door. “Go away, I never knew you” will be the words of the surprise. The test will not be if you are protestant or catholic, Calvinist or Baptist, etc. The test is does he know us, not that we know him (though that will most likely be true also.)
In the mean time “working out our faith with fear and trembling” apply. Not the other persons faith.
We will find out soon enough who is right and who isn’t, so place your bets.
The point is that if one believes in fairy tales, other than the true scriptures that God wrote to us, the odds are very high that they will be believing the false Christ that is sent here first claiming to be Christ.