Lucky Gunner has among the best details and data for ballistic gel ammo testing (https://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/) that I have seen.
Original HS was often issued ammo back in my LE days but Lucky gunner tests show that it seldom expands properly and over penetrates.
HST seems looks to be improved and competitive with the other mainstream ammo brands (Remington, Winchester) that hits the sweet spot of large expansion and reliable 12-15" penetration.
Just watched that. They didn't test the 158gr hydrashok in .357. They had done a .38spl&357mag test.https://www.luckygunner.com/labs/revolver-ballistics-test/