Comment by umpalumpaaa

2 hours ago

Sandboxed Mac apps have access to their own container which includes directories like Documents/ and a temporary directory and more where they can save anything just like on iOS.

That’s not quite how macOS sandboxing works. Users expect to be able to save and open (non-iCloud Drive) files in ~/Documents, not in a containerized silo. If the app uses NSOpenPanel/NSSavePanel, those work with the system to grant the app a sandbox extension to the location the user chooses in the open or save panel.