This is true because the realm configuration syntax changed slightly in 7.0 for Elasticsearch and it is not very easy to document for Elastic Cloud as it supports multiple versions of Elasticsearch. We are working on it and we will update the documentation accordingly.
Defines the SAML attribute that is going to be mapped to the principal (username) of the authenticated user in Kibana. In this example, nameid:persistent maps the NameID with the urn:oasis:names:tc:SAML:2.0:nameid-format:persistent format from the Subject of the SAML Assertion. See the attribute mapping documentation for details and available options
We'd be more than happy to get your feedback regarding whether you still found this unclear and why.