That latency also reduces throughout. While a freighter is anchored waiting to unload it's not carrying other cargo. We have the same number of ships, but the effective number of ships has been slashed.
It's a good observation, but it only impacts throughput when ship capacity becomes the limiting factor. If you added more ships right now (or shortened wait times), it wouldn't change throughput.
Do people allocate emergency space on sea pods to free ships ?
What's a sea pod?
some term I made up to describe temporary floating ground area (polders ?)
There are barges which could hold some cargo temporarily. But there's no practical way to move most cargo from a freighter to a barge without the type of large cranes found in ports. There are only a few floating cranes in the world large enough to even try.