I seem to be the only person who uses the word secularism in a different way. To me it describes the concept of separation of church and state - sometimes also called Laïcité. I think the article got translated in a bad way. The original talks about unbelievers, which the Germans also use in the sense of non-believers.
A better word would be non-deitism. It's not only semantics, as these are two different concepts which
may overlap. A secularist can or can not be religious, a non-believer is not.
So, in this context: secularism is more ethical, non-belief not necessarily.