Duplication glitch with furnaces and smeltable items

I saw this video of a duplication glitch. It involves furnaces and smeltable items.

Steps for reproducing this glitch:

        1. Have 1 stack of the item that will be cooked in your inventory. 

        2. Place a stack of the non-smelted item in the furnace and wait for them to             

        3. Once a few items are smelted, place the smelted items onto the stack of the same items. 

NOTE: This works on touchscreen ONLY.  It does not reproduce with a keyboard and mouse and controller.