Jay Beckman wrote:

Given that the PIC is ultimately responsible for the safety of the flight,
how (if the person under the hood is the PIC) does this flight legally
maintain Visual Flight Rules when the PIC does not have any Visual?

Ultimately responsible does not mean SOLELY RESPONSIBLE. The safety
pilot need not be PIC, he has see-and-avoid role, but "IN COMMMAND"
entails far more than that.