It is a religious option in the same way any other faith is
No, it bloody well isn't.
Do you build atheist temples to get together and pray to nothing in?
Do you preach the Word of No God to the people?
Do you build shrines to Richard Dawkins?
I don't like it, I don't like its historical ignorance nor do I like the fact that realms are disadvantaged by not having a state religion, I don't like how your historical education is so black and white its almost a bad joke. It would be hard, dangerous, would make a pariah out of any noble or realm that took it upon them but its certainly not imposible for athiesm or expecially agnosticism to exist in your settings. Nor will I stop reminding you of that fact when the subject arrises.
You don't have to like it. And it's not my rule, or rooted in my education. It's Tom's rule, and in case you're unaware, he's actually one of the most hard-line atheists I've ever met. He just knows how dumb it would have been to profess any such belief in 1324.
The game doesn't—can't—simulate a peasant mob taking you and burning you at the stake for admitting to this insanity in BattleMaster. If it could, we could probably dispense with the ironclad "no atheism" rule. But as it stands, the game just doesn't have the AI to do that.
So you'll have to be content with a "no atheism" rule, rather than simply having your character die for trying to be publicly atheist, as would be more realistic.
