Is read-only access sufficient?

[Mikenux]

Is read-only access to files by an app sufficient as file protection, if the app must request write access to the files?

I'm asking this because, to better protect files in folders that a user has given to an app, I would have liked an option in the UI telling users that they can select a single file instead of a folder, for example to see what the app does. However, this seems hard to convey to users, users don't particularly want to "test", and it can add more clutter to a UI.