i guess the decision point for an artist is, “is there greater cost to get surface information from a normal map, or geometry?”
it does seem stupid to have a concrete brick have millions of triangles. But what if you desire a high resolution for the surface details. Would a 2k+ normal map cost more than the nanite geometry which negates need for normal map?
And also there is factors beyond sheer optimization. If one workflow is easy and fast and the other is arduous, you can consider times-savings cost as well.
I didn’t look at the assets in question, just making some broad points about nanite from what I understand about it. I still havent downloaded ue5 yet and probably wont for another year though.