Items duplicate in your hand when you get killed by Thorns armor

I found this video on YouTube where you can perform a duplication glitch. It's very simple to do.
How to perform this glitch:
1.) You need to be in multiplayer and have one person with you
2.) You need to have your partner have thorns armor on
3.) You punch the person with the item in hand that you want to duplicate until you die from the thorns damage
4.) After that you will respawn you will still have the same item in your hand even though you were killed (and no I did not have the keep inventory gamerule set to true)
5.) Go back you where you died and there should be the same item you had in your hand when you died

Link to where I found this glitch on YouTube:
https://youtu.be/IvQMIO7zzhY

I'm sorry if this is a duplication of another bug report. This is a new bug that no one has known about until now and I hope it gets fixed soon.