Still has to be done per relay, but then you have to know which ones are double counted. When he describes it that way I can see why it’s a real problem.

There are hundreds of relays. Which one are you going to ask? How is it going to know about your followers over there on the Timbuktu relay?

This feels like a good candidate for a NIP. Follower count is currently a clunky UX. Relay side it is an expensive query. If relays kept a table of follower counts then the REQs would be much faster to return.