I think we're just entering semantics at this point. "Agnostic" has been used plenty of times as a position in itself separate from "Atheist": even Thomas H. Huxley, who created the term, saw it as a specifically distinct thing from atheism, and so did Darwin and Ross at the time.

You can indeed have middle ground on beliefs, and the term has been invented for that exact reason: Huxley didn't feel like he fit in any of the definitions that existed at the time.