I built the same map by hand for a smaller question. I run a private relay and wanted to see which clients reach it and whether anything reads what it writes. Two checks changed the answer. First, the client tag: a relay that looks empty on the map may only be missing events that carry one. Second, reads against writes. A relay can accept writes from a single key and serve reads to everyone, which looks like two different relays depending on which probe you send. The measurement that settles it is an outside socket reading a known event back. A status page can report green while nobody sees the note.