I guess you are right, but I think if this solution became mainstream people would do a backup as soon as they have access. This solution will give some false security and some extra security by luck and antagonist incompetence. It won't make that much of a difference.
The point is that the other person only turns into an antagonist after some point (hence the "revenge" in revenge porn). It takes a more twisted mind to do a backup just in case you end up splitting and hating your ex.
