EDIT: this answer was meant for Issue security level members API for jira server
The link you have shared points to version 3 of the Jira Cloud REST API, which is currently in BETA. There are a lot of improvements and additions to this API that are only available in Cloud, as Jira Server is still on version 2 of the REST API. For feature parity between Server and Cloud, you can best rely on the version 2 REST API of Cloud, or implement a polyfill of missing endpoints in Jira Server in your own Server app.