Error: This API action is not available for Engines based on an Elasticsearch index

[dysproseum]

I am using the Drupal module elastic_enterprise_search and am connected to an Elastic cloud instance which is running its own engine.

When I attempt to reindex content, the API returns Error 400 Bad Request from src/AppSearch/Endpoints.php

However, via the console, I was able to get a more specific error message.

What causes this error and is there any configuration I can do to resolve it?