You are, like so many other posters, talking about this is if this were a dispute over some matter of fact, rather than a semantic dispute: it is not as if people come pre-labelled "atheist", "agnostic", and so on. Even how people self-identify is dependent upon how these labels are defined. So the question here is not whether atheism and agnosticism *really* overlap, but whether we should define these terms "atheism" and "agnosticism", so that they overlap or not. I say no, and I've said why; its unnecessarily ambiguous. And I've been
unable to get a straight answer from ANY of the proponents of the view that atheism should be regarded as LACK of theistic belief as to what, if anything, is gained by
that definition as opposed to defining atheism as
belief that theism is false- a definition which does NOT allow overlap between non-theists, atheists, and agnostics.