Lunal'Valgoth's Girdle

Not sure if this is a bug but I just remembered that I got dropped such a girdle and it was not dropped by an enemy with that name.
Now this is a bit fuzzy here but I believe that Lunal’Valgoth was the enemy that “guarded” the cultists that were imprisoned in the void but that I got that girdle dropped by the boss that guarded Ulgrim.
So, assuming that I’m not mixing things up here - is it intended that this item, seemingly named after a mob, is not dropped by that same mob but by another one instead?
Or can they drop from different enemies?
GrimTools refers to the mob that drops it as “Gabal’Thunn”: