Something this old and unchanged should be considered done and perhaps even bug-free. Unfortunately the state of software seems to be pursuing constant change instead of stability.
That's a lot of work for something pretty much nobody uses. And in the end the SysV FS support might not even work anymore because of oversights during the API updates.
"can't even properly test it anymore" almost certainly means not that it is impossible for the maintainer, but more like they have better things to spend their time on.
Well... Then, if it builds, it can at least be tested with the same tools that test every other filesystem.
[1]: https://www.phoronix.com/news/Linux-Floppy-2021-Regression