Different strategies for the fall are appropriate for different players depending on their circumstances.
What would his reasons be for pitching this fall? Does he expect to do better than he did this spring and summer? Does he think his recruiting options will expand if he does the same thing he did this summer in front of a wider audience? Is he itching to measure himself against better competition?
Are those reasons more important than using the fall for arm rest and conditioning?
You already laid out the case for what you think your son needs to do.
Best wishes,