Since 1.12, items inside a crafting table, an enchanting table and others don't drop to the ground anymore when the interface is closed but go back into the player's inventory. This doesn't happen when leaving the trading GUI.
For example, if I put paper in the very left slot and close the interface, the paper will drop on the ground. I expected to see the item go back into my inventory. Hence, this is inconsistent with the other GUIs.