the effect of SG is different from airplane to airplane. It is more pronounced on aircraft with a trim tank.
The fuel loading logic on the A300-600 is that fuel is only loaded in the trim tank when the inner / outter / center are all full. So depending on SG, for a specific KG load, you may or may not have fuel in your trim tank. This has a big effect of TOW CG.
On the A330, the fuel loading sequence is automated, such that fuel is dristributed to all tanks as per a set algorithm, which limits the CG shift. However around the 36 to 38 ton fuel load, the last ton or more of fuel solely goes to the trim tank. So again, for a Block Fuel of 37 tons of fuel, SG does play a significant part.
Yet, the FCOM is clear. Enter ZFW & ZFCG, and go.
The SG effect on CG is only important in determining if you are inside the envelope. It is not important in terms of Stab Setting.