And yes it's based on kind 3 events, but not the P tags (that's contacts) but the relay list held in the note content.
Discussion
Ohh ok, that makes more sense. Which relay do you fetch these events from then?
I gather the events from a bunch of the most popular relays. I did the first load of events from Jan '22 'til yesterday, then counted up which relays in those events were the most popular, then re-gathered the events from all the most popular relays.