Files takes an extension (plugin) approach to files, and is decidedly non-Posix since it was focused on supporting remote/slow file sources first. iCloud, WebD

Files takes an extension (plugin) approach to files, and is decidedly non-Posix since it was focused on supporting remote/slow file sources first. iCloud, WebDAV and CIFS (as well as On Your <device>) are examples of support that Apple ships first party, while third party extensions include Dropbox and OneDrive as well as more exotic things like emulator file systems (iSH) and SSHFS. Before Files came out, every app that wanted to integrate with DropBox had to ship a dropbox SDK which included people logging into dropbox through each app, individual developer API tokens, etc. Now the user just installs Dropbox and it works. The challenge for Dropbox has and continues to be being a product and not a feature (with a nod to Steve jobs).