Ahhhh, the mystery of Sungold. Yes, I have had several volunteers over the years but though some have come close, they are not the real deal. I think their parentage is an iron-clad secret that will never be revealed.
I grew Esterina F1 this year, very pleased with the production and taste, but to me and others who have tasted it (I gave 4 people plants), the sweetness, while very intense and nice, is somewhat one dimensional. The fruity, hint of pineapple delight of SG is the golden grail. That said, I will continue to grow Esterina again next season as I liked it.