Context is important here, you are unlikely to get the wrong fuel when there is only one pump, it should have been checked before the tanker was allowed to put it in the tank.
OTOH when there is a row of 3 pumps each with long hoses lying on the ground it is very easy for mistakes to be made. I once found that the hoses for the 80/87 and 100/130 pumps had become crossed and the nozzles hung on the wrong pump at FAGC in the 70s. The scary bit is that the 3rd pump was turbine fuel - potentially nasty.