Unlike hunts in the overworld, NMs in Eureka do not have "classes" (B-Rank, A-Rank, S-Rank) and therefore do not fit into the framework for these achievements. First they would need to classify each NM with these, which I don't think fits with the way they're designed. Also, it would completely undermine the whole idea behind the hunt achievement since its meant to be a long-term goal. Everything in the game can't be instant gratification, if it were then you'd play a week and be done...