REST API Get Single MR returns undocumented detailed_merge_status

I’m using the REST API Get Single MR endpoint to check if a merge request can be merged using the value of detailed_merge_status. I noticed today that one of my requests returned a response with detailed_merge_status set to preparing, but that status is not documented. Looking through Gitlab’s code base I found this enum file for detailed_merge_status which includes preparing. I was wondering if there is a reason that this value for detailed_merge_status hasn’t been documented.

This happened when making requests against a self managed GitLab Enterprise Edition v16.4.2-ee instance.