And yes, Grav and Cockpit are self-hosted flat-file CMS, but now that you ask makes me confused. I was under the impression that Lektor was similar where you have a flat-file CMS and whenever a change is made, the static files are created.
My second guess is that this actually a CMS that exists locally and deploys static files when a change is made?
The key addition is that there is a nice UI for adding content in the system running locally, so it can be used by less technical users that might not feel comfortable with writing in text files with special tags/metadata, as traditional static generators require.