The ships are unloaded ASAP. Cars do not just sit on them. One of the reasons for delays in docking is to ensure the port has the capacity for the ship to unload. After that it depends on available parking next to the port, whether quarantine cleaning is required and what the supply of transporters to move them to distribution centres it.
A bad example is my car in Sydney. Arrived at Port Kembla late March, I won't see it until May 4th - ~6 weeks sitting in Autonexus car lot behind the huge load of Teslas from the ship before them.
It is chaotic in our ports at the moment and most of not all of it is totally out of Tesla's control.