Sounds like a design issue, no? If Apple implemented it, they'd call the feature "Secure Liferaft" or something equally silly, but I have no doubt in my mind that they could engineer a proper solution for it. Today's users go out of their way to hide files and folders, so why not give them a chance to do so the right way? The technology is there, all you need is a little marketing pizzazz and a 30 second ad spot with Billie Eilish in the background.