I really appreciate that you put that in context -- i.e. the position of that result in regards to AI history.
“4-stone handicap” can seem odd or artificial to non-Go players, but it is a classic way of balancing a game between players with known different levels: because of the complexity of the game, mastery expands wide, and it is rare to find a player exactly at one’s level. The gameplay changes a bit when starting at an advantage, but not significantly. For PR reasons, AI advances are usually measured with matches against star players; that handicap tradition allows AI advances to be measured more finely -- and I guess have a count-down, more appealing that the ‘not beaten yet/OK, we are done’ dichotomy of Deep Blue vs. Kasparov.