This warning at the top of that page:

Creating Local Atlas Deployments with Docker Compose is available as an experimental feature. The feature and the corresponding documentation might change at any time during the experiment.

It is a MongoDB database server at the core but this is a new feature to have a local “Atlas” deployment. Since it is subject to changes, I cannot say if it is production ready.

You may check the docker image content to see what happens in it if you know how to inspect docker images/containers.