Are you asking if he should write about his grades vs his ACT score in any of his essays? If that is your question, I would say…NO.
If there is some compelling reason why there is this (small) difference (major illness or something), let the counselor deal with that in their letter. Anything your son writes is going to sound like he is trying to make an excuse for his grades. That shouldn’t be the subject of his essays.
There are thousands of colleges in this country who will welcome him as a student.