Applications do not need permission. The user that is currently controlling the application needs to be able to use that application to read and write files but

Applications do not need permission. The user that is currently controlling the application needs to be able to use that application to read and write files but there's no reason that the application needs access when it's not in focus and, with the sandbox model in Catalina, applications have the ability to ask for explicit read/write permissions without prompting the user if they've already given access to install it. The biggest protection here is that the folder is shared via iCloud in most instances. Asking for explicit permission is really the only way to do that safely.