While I agree this was extensively discussed elsewhere, still, the wording is pretty clear on the SA website.
As a Gold Status holder you can choose not to travel light. We allow an additional 20 kg (44 pounds) where the weight concept applies, or one additional piece of luggage where the piece concept applies.
Zero + 20 is 20 and zero + one is one.
The only way to argue here is that neither the weight nor piece concept apply. Which is not what I would expect anyone to assume.