There is a very obscure undocumented api in macOS for detecting if two files are equal block-by-block but yeah I don’t think most tools can tell when files are clonefile’d

Just a note on your documentation: it says "this benefit does not extend to macOS" about saving disk space. I find that to be slightly misleading. Since arguably the most common FS for macOS is now APFS, it does save significant disk space unless one were to modify the node_modules files.