The leak test was done earlier by blasting compressed air from the inside and soapy water on the outside - 2 person job. Maybe not 100% accurate, but it should have shown any significant leaks.
The certified buoyancy foam is in sheets, and it sits above the stringers. Thus any water can freely drain out through the limber holes.
On alloy boats apparently you do not pour in PU foam, it reacts with the alloy.
There are a few more pieces to weld in, the motor and basic controls, then it will get a splashdown prior to finishing.