(I must admit I haven’t read the whole thread, so I apologise if I’m missing the point.)
I mean, really calculate the prefix sizes for the groups, and how long of prefixes people are finding for bitcoin vanity addresses?
The “prefixes” were never meant as a proof-of-work challenge. The RFC has nothing to do with proof-of-work, it’s just a suggestion to reorganise nodes differently into groups, and with that new organisation, the common prefix is simply the obvious choice for a group name.