Can I just tell him that his brain learns movement tasks differently? That these are things the OT (who he really liked) said to try? Or should I give more detail?
I'd start there. If he wants more detail, give it.
This is not ideally a "big reveal"-- it's ideally more like "here's a thing we know" where it can be discussed on many occasions over time (as a taken-for-granted fact) whenever he needs the information.
My kids find it very very good to have names for their challenges. Not just "I'm not good at this" but instead "this is challenging because of X and I can work around it by doing Y."
