Thanks for the detailed response Jeremy, it is much appreciated. On close inspection, the studs are round but some of the pearls on the strands are slightly off-round.
My mother purchased a big strand of these pearls 10 years ago and had it made into a necklace and two bracelets, and then she also bought those studs, and they were all sold to them as SSP. I found the "certificate of authenticity" to prove it. Obviously they were misinformed. My only consolation seems to be that this so-called Naga Pearl Farm appears to be permanently closed.
That said, can you speak to the quality of the freshwater pearls? Are they decent freshwaters at least? They are all 10-11mm and seem to be well matched with relatively few imperfections and decent lustre when I look at them in natural light.