Identity Protection alerts now available in Microsoft 365 Defender

Are Microsoft Defender for Identity alerts supposed to be only available in the Graph APIs?

We don't seem to be able to retrieve MDI alerts through the API  (https://api.securitycenter.microsoft.com/api/alerts).

Neither when attempting to get the alert by it's ID: https://api.securitycenter.microsoft.com/api/alerts/aa7e3fef8d-867e-4f21-9b26-5fcc736aaced
nor when using a filter (https://api.securitycenter.microsoft.com/api/alerts?$filter=detectionSource eq 'AzureATP')

The filter value of AzureATP seems to be a valid filter enum value for the detectionSource, but doesn't seem to ever return alerts from Microsoft Defender for Identity.

I would appreciate some help. We are not yet integrated with the Graph API and are still relying on the older one, so moving to the Graph API to get the MDI alerts would be a significant cost.