I'm not sure if it's intentional, but I had a copy of my world I had been playing for a year. I made the copy when the 1.18 update came out and when I tried to join my world it said warning and it gave the ability to copy the world via an on-screen banner. I made a copy using it, but when I deleted the copy just getting rid of junk worlds, it deleted my world entirely, all of the copies and the world itself.