It’s not a bug and that is clear if you don’t use the documents folder as your example. When granting specific access it is not the same system as when granting general Documents folder access.

The UI just doesn’t reflect this.

> The UI just doesn’t reflect this.

That's the bug. Either that or MacOS has two separate/distinct mechanisms for managing permissions, which would be a huge security flaw.

MacOS has two distinct mechanisms. One gates access to Desktop, Documents, etc. for general access. The other grants access through the Open dialog. The open dialog is always superior because it's consent for a specific location.