Just because you find something incredible doesn't mean that it is. I find this position perfectly credible and ordinary, because it's the position that I hold. I find it incredible that people get themselves tattoed, but I know that others hold contrary positions to mine.
And that's okay.
So, let's concentrate on this and only this point, to get it out of the way, because I think in this case, it can be a discussion based solely on logical arguments.
What you are saying is that someone can be an atheist without knowing they are an atheist. To me, one requisite of holding a position is that one must be aware that one holds such position and a mental justification of it. When I say justification, it can range from I just want to to the most complex dissertations.