My girlfriend and I started a shared world, we are on the same wifi network and both have Xbox series X. She made a new save and made it a shared world she gave me and another friend who was also on a series x access. After day 24 I started hosting the world and since then the save has been acting like a regular multiplayer world for me. The world is showing back up saves, but not letting me create standard copies it will also let me try to make the save a shared world. For everyone else the the save shows that its at 24 days still and that save in my backups list is the only one I can create a standard copy save for.