Perhaps whoever told them that is the one that's confused.
I've been here since 2011 and it's always been designed to be open to people of any belief, long as they respected the rules of the site. They've never made a single attempt to isolate or segregate such people.
But, really, what's to stop them from posting anywhere they want either way?
My understanding is if a person is posting blatantly unchristian ideas for the purpose of Teaching those beliefs, then report them. If they're posting a theology that differs from yours, don't bother. So if you see someone posting OSAS and you disagree with it, that's not a legit reason to report someone. If they're posting about other religious beliefs, or openly against Christianity, then that's reportable.