I don't think we can confirm that one way or the other, since undrilled pearls can also be dyed and since FWP are now being cultured with a bead nucleus.
This is what I suggest: look at the other pearls the seller is selling as SSP.
Be suspicious if the pearls are colors that don't occur naturally in SSP but do occur naturally in FWP (like pink, peach, lavender).
Gray is not a SSP color. They could be Tahitians or dyed FWP. Be suspicious if the price is too good to be true. FWP cost less than Tahitians or SSP.