What's the use-case for it?

It's primarily useful for integrating things like Buildbot with Pagure, where it tends to want a lot of data to present a holistic view of things.

I'm working on a pagure integration in nvchecker, matching the gitlab API:

Ref: https://github.com/lilydjwg/nvchecker/blob/master/nvchecker/source/gitlab.py

it would be interesting for psss/did reporting