Disenchanting Loot From Season 1 Heroic Dungeons from older Expansions gets you the Enchanting-Materials from those old Expansions.
At this Point i am not even mad anymore, i´m just legitimately curious what exactly is going at this Company.
Saying that you are not even trying anymore is the understatement of the Decade…
Btw: Cloths drops were also not updated.
Given the plethora of cloth drops (especially Dusk/Dawnweave) in ths expansion, this is just a minor inconvinience of course ( /s, just to be sure)