AshleyJPEG

I’ve tested this in multiple versions, and it seems to work in every single release version, and even beta, and it works with regular chests:

26.1.1 - Bug occurs as stated.

1.21.11 - Bug occurs as stated.

1.12.2 - Bug occurs as stated, although is much harder to achieve as holding the number key swaps much slower.

1.7.2 - Bug occurs as stated, although is much harder to achieve as you must click between the items quickly rather than holding a button.

1.5 - Bug occurs, though the overwritten duplicated item is truly a duplicate, not a bugged version of the block, and will stack with the original.

1.0 - Bug occurs, even in a version before trapped chests were implemented, can be done with a regular Chest and a block of TNT, creates true duplicate much like 1.5.

Beta 1.8.1 - Bug occurs, though the duplicated item cannot be picked up at all.

Can confirm this works, holding the '9' key to quick swap the two blocks make it a lot more consistent (still only works about 1/4 of the time)

It seems like less of a duplication glitch and more like it temporarily replacing one block with a copy of the other, since picking up the dropped block doesn’t automatically stack with the one in your hotbar, and

placing down the glitched block, or moving it around in your inventory returns it to its original state. It also works with blocks other than Podzol and Grass Blocks. Also works in both survival and creative mode.