Right now, there is no supported way to get per-user Copilot premium request usage for an organization via the REST API when that organization belongs to an enterprise.

Even though the REST API shows a user query parameter, GitHub blocks its use for enterprise-owned organizations unless the request is made at the enterprise level by an enterprise owner or billing manager. Organization-level admins and GitHub Apps cannot use this filter for enterprise orgs.

So what you are seeing is expected behavior:

The API technically supports the user filter.

But GitHub disables it for enterprise-owned organizations for permission and data-visibility reasons.

This limitation is enforced by the platform…