I agree atheism doesn’t entail a particular cosmology. An atheist can be a naturalist or a dualist or a pragmatist, for example. Plato was technically an atheist.
But in practice today, the best nontheistic rival to theistic cosmology is science-centered. That means the atheist is stuck with methodological naturalism, and that’s what generates some absurdity on the atheistic side, as I argue in the article.
You might be interested in an article I wrote on this issue of ultimate explanations, called Reason, Attitude, and Ultimate Reality.