HST does not stand for Hydra Shok Two. It might have at some point in the development process, but Federal has never termed it as such and it's an entirely different design other than the company. If anything it could be seen as a Hi-Shok successor.
At this point, though the idea that HST = Hydra Shok Two is so affixed due to the popularity of the Hydra Shok branding that there's no point in arguing it anymore, much in the same way that Kleenex now = tissue paper.
In my opinion after review of the evidence, testing, and street performance records, HST and Gold Dot are substantially better choices than Hydra-Shok. If all you can get your hands on is Hydra Shok, it's still a capable and proven round, just a generation behind current tech.