Nightmare Nests are likely Kuro's way of "softening the load" for new players, so they don't have to worry about wave plates, this will make a significant difference in a few patches when you can clear five fields and collect all the new echo types instead of focusing on just one type at a time.
The real pain in the ass is not having a way to farm these outside of the nests, and the ones available share the same pool with two other echo types.