For chess, it's supposed to be a purely intellectual game, and even though there are categories, the top women can play with the top men. This wouldn't make sense in 100m dash where the Women world's record is beaten by highschool boys.
Essentially this places the entire human species in a second-tier category. Human champions are now good, "for a human". Humans are in the lower league and we must make sure they only play between each other because of their inferior cognitive capabilities. They are no longer competing for the genuine title of best chess player in the World, they wouldn't even qualify to enter the tournament. The World best human in history can be beaten by the equivalent of a highschooler machine player.