Simply because it’s a commons, and I like that, I’m going to use definitions from Wikipedia.

I think we differ on what a world view is. Secular Humanism is, to me, more accurately described as Wikipedia describes it - a philosophy, belief, or life stance. These have to do with what you identify with, or values and ideologies you live by. And yes, secular humanists need not be atheist.

A world view is much more broad than a philosophy, belief, or stance, or the having or not having of any particular belief.

So yes, atheism is not a world view. But one can have an atheistic world view, without atheism being a world view. The world view and the individual who holds it are not defined in total by any particular facet of that world view, any more than “a brown-haired person” or “a person who has no cats” are complete descriptors for any single individual.

So “an atheistic world view” simply references one of a large number of world views, all of which fundamentally lack a belief in gods.

Yes, lacking in a particular belief does not define you as a whole person. I would not expect that it did, even if you held atheism as a belief, as in the less broad senses of atheism as defined on Wikipedia.

If I don’t believe in unicorns, it totally makes me a non-unicornist, which is clearly only relevant when discussion or actions come up that involve unicorns, like when I’m posting in a non-unicornist or unicornist context. But it doesn’t necessarily make me an anti-unicornist.