Yes, as pointed out earlier, It's a legal requirement in Europe that all de-refueling
while pax are on board must be supervised by a responsible person. Most other airlines have longer turn round times, and pay a little more to the agent, so the dispatcher will be responsible. In most places the agents will also have some agreement with the refueling company and they may take on the responsibility themselves. So it is down to two things, time and money. Quicker and cheaper to get the crew to add it to their long list of responsibilities.
I hope the captain wasn't on one of their lovely new Brookfield contracts as he may well get the bill for all of the disruption, and fuel!