It's not so much that his processing speed is too high for his abilities that would be the problem, but that, if the WPPSI-IV results are to be believed, most of his reasoning abilities are in the Average to High Average range (though matrix reasoning is Superior, which is a good score), suggesting that the Full Scale might overestimate his learning potential, due to his high speed.
His CogAt verbal is pretty much in line with the two WPPSI verbal subtests, taking into account that it is one grade out of level.
I think the evaluator's main concern is with, based on this evaluation, potentially placing a cognitively high average student into a program designed for superior-to-very-superior cognition.
Now whether these scores are fully reflective of your DS's cognitive ability is another question, especially where there is suspected ADHD.
