I don't know if it's for survival mode too. Anyway the dupe is that if your on a donkey with stuff in its chests and log out riding it; it will dupe (the donkey) as well as the items in the chests. I don't know about horses or mules though (I'm talking about the grey one. so I don't know if that's the mule or donkey I could be wrong). (by the way I private messaged this because I don't want anyone to try and dupe thier donkey or mule and their diamonds too. XD :3).