Or if it walks like a duck..... Or Sanya plays lip service to it for his own reasons, but the Almighty and the angel in charge of his Sword knows what is really in his heart. I suspect the latter..
He doesn't have to believe.
He just has to be really, deeply, good... all the way down (and strong enough to bear the burden).
Just like Butters, whose Faith is evidently Jedi not Christian.