Of course they went with classic models.
They're flat fucking textures easy as hell to make new cash shop items that are just literal flat textures that wrap around a model. Hell you could probably ask an AI to make a texture for a classic Everquest model and it would be able to vomit one out quick.
Luclin Model animations were ass compared to the vanilla but the armor was so much better looking, but it was also layered armor. If you wore plate armor you had chain armor under the plate, you could see it when a corpse despawned the plate armor would despawn first. If you were wearing leather or Chain when your body despawns your character becomes naked but not textured so they're just skin colored.
Luclin models require a hell of a lot more effort to create cosmetics for.