So it's a fork but with somewhat semantic diff specifications?
Yes, specifications which could almost certainly be applied with a custom merge drivers or strategy rather than trying to come up with a clever name and hand baking a custom toolchain to do what you can already do with Git
Not all projects use git.
Weird.
How many of those projects are attempts at maintaining patches across multiple upstreams, where none of those upstream projects use Git? The author freely admits in their post that all upstream projects in their case are using git, like most of the FOSS world. They just chose fossil for their downstream project because Reasons.
The TeX source works like this, too. There is the original tex.web and some change files which get applied when converting it to either a TeX document or pascal source. (These days the pascal is further translated to C.)