It’s inexperience as most of their teams haven’t done any persistent multiplayer of any kind and they tried to bolt this onto the single player game engine. Preventing duping is actually non-trivial to solve if you haven’t designed all of your systems to be fully transactional and atomic. A lot of the issues I keep reading about just don’t surprise me. The engine was not built for multiplayer, and the game wasn’t built by devs with a lot of experience on persistent multiplayer (let alone normal multiplayer).