Double tapping an item in the inventory or in a chest doesn't group all the items of the same type into one slot.

How to produce:

• Start a new creative world.
• Place down a chest.
• Pick a stack of a random item from the inventory.
• Spread that stack on multiple slots inside the chest.
• Double tap one of the slots with the item in it.

You'll notice that instead of having all the items regroup into one slot, nothing happens.