a belief system isn't one belief; whether theist/atheist. its an amalgamation of beliefs/disbeliefs. the person identifies the foundation of their belief by labeling it.I would absolutely agree. Atheists have belief systems, but atheism isn't one of them. A lot of atheists carry with them the belief system that reality is objectively real and can be reliably observed. Atheists also tend to believe in things like loving their family, loving their spouse, being kind to their neighbors, leaving the world in a better place than when they came into it, equal rights, adding to human knowledge, and many other beliefs. But, none of that is atheism . . . or apleprechanism, that is.
beliefs aren't necessarily reality, nor are they evidence based on absence of evidence. no matter how you cut it, its a belief system without some level of proof. there are no absolutes even in science. there is what we know and what we believe. what we know is mutable and so are beliefs.