It was quite a cultural shock for me when I first met Americans vehemently claiming that Catholics aren't Christians.

In a fantasy setting I would actually expect a religious person to know a thing or two about their religion. Only in a fantasy setting though.

I was raised Mormon, and had always been taught that if you get to the highest heaven, you'll become a god and make your own world. Only after I left did I find out that that's not actual doctrine and comes from taking something that's supposed to be a metaphor literally. And any details about the church that look bad aren't going to be repeated by mormons, so mormons tend not to know about them.

Right, but... while the requirement for INT supports "cleric who doesn't know anything about their religion" it also makes it significantly harder to play "cleric who does know something about their religion" - which probably should be more viable than "the wizard happens to know all this stuff randomly"