Safety Concerns
You just don't give up, do you ?
Pilots, Radio Officers, Navigators, Flight Engineers, were known collectively as the TECHINCAL CREW ( Tech Crew for short ) as opposed to the CABIN CREW or TRAFFIC STAFF.
In the days when we had a Flt. Engineer, he was responsible to the Captain for ensuring that the correct fuel load - as decided by said Captain - was on board, and before signing the loadsheet and thereby taking legal command of the aircraft as Pilot-in-Charge, I would confirm with the Flt. Eng. that that was so, I didn't care who, or how, other parties responsible for ensuring that happened went about their allotted tasks, but if the figure was wrong, and sometimes it was, I would take responsibility for delaying the flight, and with the TRAFFIC and TECHNICAL CREW decide what action to take to rectify the situation.
The decision on how much fuel to carry, and ultimately ensuring that that happened was the responsibility of the TECHNICAL CREW, if a delay occurred as a result, then it was a TECHNICAL DELAY.
As the pilots have finally taken over the other TECHNICAL CREW jobs, including that of Flt. Eng. ( mistakenly in my opinion ) then the Captain or F/O now fulfils that role, and clearly all airlines set their own policy in that respect, but it obviously must rest with one of the TECHNICAL CREW to do that confirmatory job, and finally of course with the TECHNICAL CREW Captain to make the eventual decision to go or not to go.
QED, end of story, now looking for the "Ignore" button.