Duplicate Boots (Chain, Iron, Gold, Diamond)

I just wanted to build a trap...
1. I was in gamemode 1 and equipped a full diamond gear
2. Then I switched to gamemode 0
3. After that i opened a Trapped Chest
4. I then had two pairs of shoes in my inventory

It tried it with different types of boots(you don't need a full gear)
It worked with all types except leather boots...

Be carefull! Just open your inventory, in gamemode 1, equip your boots with shift. Then close it. Switch to gamemode 0 and open the trapped chest.

DON'T move! If you move only one block it will not work!

All steps are shown in the attachement.

Have a nice day.
Fabian

Please contact me if this is a real bug/glitch or if it helped you to improve the game.