It is a library you import to annotate your code. Most APIs do have a service layer that need some form or orchestration. This library makes the service layer automatically orchestrated.
Your workers too can import the library and have embedded orchestration.
In process durable execution gives you freedom for a lot longer than having to hire Airflow or Temporal. You just need postgres (which you likely already have)
How'd that work in a microservice architecture anyway? Does each service has some part of the orchestration logic defined? Or will I end up writing a separate orchestration engine as one service anyway? Wouldn't that then contradict the promise of the article?