Aetherytes, Garleans, and You!

[Jingai]

I'd also point out that Regula van Hydrus is shown to use some manner of teleportation during the Warring Triad quest chain. So there's direct evidence of a Pureblood Garlean making use of teleportation - though I'm inclined to believe he simply attuned himself to the magitek gate overlooking The Gration in Ayzs Lla.

Could be that Hydrus simply had his armour outfitted with some sort of magitek field generator that could duplicate aetheryte teleportation effects. I'm not sure Pureblood Garleans can attune themselves to an Aetheryte like other Hydaelyneans can.