Paraphrased from Wikipedia: "A function looking up a customer's name and address in a database is typically idempotent, since this will not cause the database to change. Similarly, changing a customer's address to XYZ is typically idempotent, because the final address will be the same no matter how many times XYZ is submitted. However, placing an order for a cart for the customer is typically not idempotent, since running the call several times will lead to several orders being placed. Canceling an order is idempotent, because the order remains canceled no matter how many requests are made."

The greater-than redirector fits that description, as it is normally implemented as an atomic write. Note that it does not say anything about optimization or efficiency. Only that the result remains unchanged.

Web developers have bastardized the term and take it to mean many things it does not because of the definition of HTTP GET, even though no GET operation is ever idempotent in the real world.

In automation (like Ansible), the term is overloaded. Something is only idempotent if it only tries to take action if the actual state does not match the desired state.

This will overwrite every time, which is inefficient.

As a plus, Ansible also notifies you which things have changed. This also enables easy dry runs (check_mode in Ansible).