No, they are included in the group "atheist."That's what I've been saying. They are included in the definition of the term "atheist".
They are included, but it's not because of their ignorance of gods that they are included, it is because there is "no god" in their worldview.
The definition of atheist is directly drawn from atheism, which is a lack of belief in God or gods. Ignorance of God or gods is another kettle. 'Ignorance of' and 'lack of belief in' have different connotations: one points to knowledge, and the other belief. Those are distinct topics. Definition is precise, so addresses the pertinent characteristic.