Well, they should have decided that before they let him in the race. How awful for the poor kid. What a message to send.
It seems they did not disqualify him for being autistic or anything like that:
“Apparently you can’t be more than 15% faster than the time you swam in your heats just in case you are trying to swim slower in your heat to be placed in a lower division’s final.”
If that is the rule and it applies to everyone, then fair is fair.