That's an awfully short route to use a ship on. I could see this being very useful for stuff like vehicle and passenger ferry transport but cargo containers seems downright ridiculous.
Their previous process was load container on truck, drive to major port, unload container from truck, load container onto a ship. The plant apparently is a small port, so the new process is load container on ship, sail ship to major port, unload container from ship, load container onto another ship. I don't see why loading and unloading a ship would be more onerous than loading and unloading a bunch of trucks. So if the ship uses less fuel than a bunch of trucks, it's a win. Why not do it?