Duping by Throwing Items as Leaving a Server

I play on a Vanilla server that has no anti-cheat and a large issue lately has been duping. After trying to get one of the people who have been dodging IP bans by VPNing to give me a lead on the issue, I found what I think is the root of the issue. When a player throws their inventory or items using a macro, hacked client, even just the throw button, then spamming chat with "blank messages" (again by a macro or client, example being .leave spam in the Impact client) to have the server kick them or interacting with themselves so the server kicks them their items are duplicated. I have tested this on the same type of Vanilla environment that I have seen this in, and understand the core idea to be shown in this video. An issue with this exploit being, it works more successfully when the server it is done in is packed with players and has some lag. I do not know if there is a way to patch the technical side of this exploit since I don't fully understand it, all I know is that it is something that the Vanilla-specific environment is vulnerable to. Thus, I figured the best method I had was to bring it here. I can do more testing and record my own videos showing the issue in action if requested. I know nothing about how this affects the server technically.