The minecraft:decorated_pot item type is missing the minecraft:container data component from it's "implicit" data components. This causes the pick block functionality to be inconsistent for decorated pots. Placing down a plain decorated pot with /give @s decorated_pot and then using (regular) middle-click to pick it back up and inspecting the two, we see
Original: {count: 1, id: "minecraft:decorated_pot"}
Picked: {components: {"minecraft:container": []}, count: 1, id: "minecraft:decorated_pot"}

This is because the decorated_pot definition in Items.java doesn't have a default component value registered for the container data component type. Every other block entity that has a "container" has a default value set for the container component type which means that after picking the block for those, the 2 components are equal and it isn't included in the data component patch for the stack.