If the Captain had been on watch and at the helm then it was his call. It seems he was down below and not in command of the vessel.
IF the GPS had been off by a few hundred feet combined with possibly miss-judging the distance of that buoy at night and things could have been ugly.
Who would have been at fault? Would the owner remember things differently to salvage an insurance claim, reduce his liability, possibly keep himself out of jail or keep his captains license?
When I am at the helm of someone else's boat I never cut corners, this includes local knowledge shortcuts that I might take with my own boat.