Vale and Uldum are not BfA zones. True story. Google blacksmithing and leatherworking "enchants" not working in those same zones as well. Blizzard screwed the pooch on this one.
From Wowhead:
"Zandalari Skinning. Permanently enchants gloves to increase the speed of skinning on Kul Tiras and Zandalar."
Sadly these new zones, while the Hyena do drop Dredged leather are not in fact the above mentioned zones.
Because they're technically not in Kul'Tiras or Zandalar.
Faster gathering should really be backed in the profession (i.e. faster gethering unlocks after reaching the expansion profession cap). The enchant cost is trivial anyway