> Reading the documentation, "this is a clone of MS-DOS" turns out to be quite a misleading summary of what this is.

Not a "clone" in the sense of 100% compatible... but a "clone" in the sense of borrowing a significant degree of ideas and APIs/syntax from it, yet also deviating at various points (whether for good reasons or for idiosyncratic ones)

It is a clone more in the sense that the Japanese mainframe operating systems Fujitsu MSP and Hitachi VOS3 are/were clones of IBM MVS: they started out as a direct copy of MVS–due to IBM having released earlier versions into the public domain, and Fujitsu/Hitachi illegally stealing the IP of later ones–but over time diverged in incompatible directions