I can't speak for kstenerud, but looking at the compact-time github page they appear to have written a solution that meets their own needs, and kindly made it a

I can't speak for kstenerud, but looking at the compact-time github page they appear to have written a solution that meets their own needs, and kindly made it available to the world for free. They don't appear to be attempting to cover all use cases (in particular, it isn't trying to be human-readable), and crucially they don't appear to be proposing it as a standard.