the minesota twin studies is one of the most discredited studies because it did not take into account that the twins were often placed in similar environments by design. There were mack truck size holes in the methodology.
Where to you get that nonsense? You can't just ignore the data on the basis of flaws in methodology. ALL studies have flaws. You have to be thoughtful enough to evaluate those flaws lest you simply disregard all observations.
Now, with your specific criticism, you have to explain (1) why monozygotic and not dizygotic twins are placed in similar environments, or (2) why if both placed in similar environments, a difference in religiousness developed.