My favorite Sam Harris quote: “In fact, "atheism" is a term that should not even exist. No one ever needs to identify himself as a "non-astrologer" or a "non-alchemist." We do not have words for people who doubt that Elvis is still alive or that aliens have traversed the galaxy only to molest ranchers and their cattle. Atheism is nothing more than the noises reasonable people make in the presence of unjustified religious beliefs.”
What is yours?
The a- in atheist does not mean non, it means without and there are plenty of words ideologies and beliefs that use the prefix a- in this context
So being non religious and being atheist are subtly different.
Even in the context discussed, there are words used in the same way apolitical, non totalitarian for example