Oh, I understand, now. You can't deal with hypotheticals. No wonder. I won't bother you after this post.
Well, if you could understand hypotheticals, I would say that the issue is your belief or lack of belief in the God whether or not it exists.
Yeah, I can't help you understand the term if you insist that there's only atheists if The God they lack belief in actually exists.
If you were able to grasp the concept of belief versus disbelief, I would explain that the particular God is irrelevant. Your lack of belief determines your atheism.
Because I don't take your view, and I believe someone can lack belief in gods whether or not they actually exist or not just like someone can lack belief in Bigfoot, regardless of whether or not it actually exists, I think when a person lacks belief in a God, whether the person is a baby r the best theologian in the world, they are an atheist with regards to any gods they lack belief in.