I guess the power here is that it can be overridden by a material instance. So If i wanted a creature to have a damage effect, I’d make 2 material instances, one with a fire layer, one with an ice layer and swap the material instance on the creature (rendering only 1 layer from a shader complexity perspective).
Seems more convenient, because I’d otherwise be using material functions with a static switch. That said I’m not entirely sure if there’s any new power gained.