Honestly never tried it because it seems to be a self-defeating prophecy due to diplomacy. Maybe if it applied to converting cities that have a different pantheon, it would be helpful. But converting cities of civs that have their own religion, they'll ask you to stop, and if you continue, diplomatic relations suffer. Even if this doesn't lead to hostilities, it blocks the ability to score RA's, which would produce WAY MORE research than this belief would.