When a decorated pot is rendered or summoned with a loot table and then a player places item(s) into said pot, no matter what items were put into pot, pot will always drop loot table no matter what item(s) was/were put in. For example, a decorated pot with a Trial Chamber loot table might drop an iron ingot and a gold ingot; even if an item, say, a Netherite Shovel, was put into that pot, upon being broken, it would only drop its loot table, dropping just an iron ingot and gold ingot, as opposed to an iron ingot, a gold ingot, and the previously deposited Netherite Shovel.