Not really. As we are seeing on the Japanese ship, rooms all share an air system, food source and the virus is likely airborne. The crew is not trained for this kind of contamination control. Every time a positive test comes up, the clock resets to 14 days. They need to be in real quarantine with correct infection control. The Japanese ship went from one passenger on the previous cruise infected to 64!
Yes, but the infection is confined to the ship. And no, the clock is not "reset" every time an infection shows up. By now, just due to the factors you cite, everyone on the ship has been exposed. But even so, so what. See first line..."the infection is confined to the ship".
On old-time sailing vessels on long voyages, there was always a surge of illnesses on leaving port, but once that passed, the surviving crew was very healthy, as they had proven to be immune.