We can hardly realistically be "SMA" about religion if we're copying medieval Europe, and it'd be !@#$ if we tried to.
SMA doesn't mean simulating Medieval European times, it means having your nobles act like nobles did in Medieval European times. For requirements on a religion being SMA by Tom is "not being obviously silly is the only real requirement I can think of."
Also I agree with Perth, they didn't just have faith in it, they thought it was a very real thing. The Pope actually hired someone to prove God's existence and he did though you probably wouldn't agree with his proof.
