I just checked the macOS / FreeBSD man page for ‘stat’, and noticed the syntax differs from the version in GNU coreutils (which is what’s used in Linux). That’s probably the only thing that would need to be changed to make the script work on those other systems. It’s on line 530.
Fair enough. But macOS has more users than Linux, and is partly based on FreeBSD. The shell and the userland tools are from FreeBSD. I prefer Linux of course and haven’t used a Mac in years, but I still think it’s nice making scripts compatible with all *nix systems.