From a real life example.
I was the FE on a flight ex Bali. The Captain and other pilots had not boarded but the pax and cabin crew were on board and fuelling was in progress.
As I did my preflight a local Fokker stopped right behind us and virtually under our tail with a brake fire.
I stopped the fuelling and initiated a pax evacuation via stairs.
Since my authority was a delegation via the Captain are you saying that I had no authority until the doors closed?
If I didn't, who had authority?
Wunwing