GAC "Matchmaking"

That’s not how the chess ratings work. They only change through play - retired players are marked inactive and ignored by the leader boards. So Kasparov still has his 2812 (iirc) rating. Also the Elo system is a little more complex than GAC skill ratings, as ratings are changed based on the strength of your opponent. Some sports use a handicap system as well - like billiards tournaments - where a lower rated player can go up based on winning a single round against a higher rated opponent, even while losing the match.