They claim to know the truth but the reasoning behind it is different between religions. I'm no religious expert but I'm very familiar with Mormonism and they push really hard on the idea that faith is intentionally separate from truth and you learn about the truth of the church by meditating on your feelings and experiencing frisson, not via logic. Yes everyone has their mythology and Mormonism has its share of things the prophet says God says but it is very different than the Christian apologists that try to reconcile the Bible with things like astrophysics and other observed phenomena.