This has happened before and I believe shipyards can run ships under some form of temporary registry before the ship is actually handed over to the owner. Even thought he ship is to be flagged and controlled by Marshal Islands, it is allowed to operate as a domestic Canadian ship "while it is under construction", without meeting Canadian registry requirements.
The radio may have a foreigh call sign while all this is going on.
Another instance of this is that the ship does not always require a pilot. The shipyard may provide its own trials master and he has a pilotage waiver for trials trips only.