Your definition of atheism is not my experience with pretty much every atheist I've ever met. It's not absense of belief, but belief that God doesn't exist. There was never anything nuanced about the definition.

Now we can say absense of belief for the sake of discussion, but then it becomes an issue of semantics, as there is overlap with agnosticism. But it doesn't match my experience at all. Most atheists will call you names for suggesting anything but the idea that the laws of physics are a complete description of reality. Teenage edgelords mainly.