No, he's not. Atheists don't believe that the answer to "Is there any supernatural force that could be called 'god'?" is "Yes." Agnostics on the other hand believe that the question can never be answered for certain. Agnosticism is completely independent of the answer. It's a statement about possible certainty of answering the question.
You're missing the point. It was said that atheism has no belief system when in fact it does; there is even an active choice what (and what not) to believe in. Those who are self-declared atheists choose to believe that life, the universe, and everything came into existence by unintelligent means. That is a belief system, and it is shared by people who identify with atheism.
Furthermore, some atheists also congregate with other atheists, and it is inevitable that culture sharing will occur and that they will come to also share a set of common moral values (even if they deny absolute truth or the eternal nature of these values). There doesn't need to be 100% agreement (or anything approaching that), in the same way that there does not exist a complete consensus among religious non-atheists on morality, but there is, without a doubt, moral sharing among a significant portion of atheists.
So, to sum up: Shared belief system, shared culture, shared moral values... atheism is definitely a religion. Even if an atheist does not congregate or explicitly share these things, it would be like a christian who only believes in his heart and doesn't associate with any organized church. Both are practicing unorganized religion, and it makes no sense to call one religious and the other not.
I understand that a lot of atheists like to think that they are enlightened and above religion (that dirty word), but logic and reason, ironically, are not on their side in this. Ironic because logic and reason (since they deny revelation) are usually important facets of the doctrine of Atheism.