Probably the main reason why fuel is put into the main wing tanks first is because on some airliners (if not most) the engines are fed directly from the wing tanks. Some airliners have to pump the fuel from center tanks into the wing tanks before the engines can utilize the fuel. So for example, if the flight requires 10,000 pounds of fuel, and each wing can hold 5,000 pounds, plus the center tank holds an additional 5,000 pounds, then you don't want to start in the belly tank, because you'll end up with 5,000 pounds in the belly, and 2,500 pounds in each wing. Then the flight crew will have to do a fuel transfer in flight of 5,000 pounds from the belly tank into the wings. Imagine if the flight only required 5,000 pounds and you started in the center tank. You would end up with the full fuel load in the center tank. When the flight crew arrives to take the plane they will have to transfer fuel into the wing tanks before take-off.
If you are topping off the aircraft, it won't matter if you fuel the belly or wings first. However, another consideration, which is not part of your question is weight and balance on the ground when the aircraft is empty. Some aircraft like the older DC8 has like 8 or 10 fuel tanks in various locations, some are forward of the CG and some are aft of the CG. However, the fuel tanks in the root of the wings are usually slightly forward of CG which helps to prevent tail tipping.