I assumed that this is intented feature; you get a much more treasures nowadays than in Col1 (or am I dreaming), where the treasures took all cargo places of Galleon. So to balance it out, I assumed that it was intentional decision to allow treasures to be placed to take only one gargo place.
Plus, considering balance, it would be waste of time to take your 1000g treasure to homeland, if the alternate option would be to take full shipment of basicly any goods you create (surely the price of the goods easily goes over the worth of any single treasure).
I don't see a problem. Changed from Col1, but imo there are logical reasons why to justify this modification (even if it is unintented).