I think you are right on the money. When he was much younger, there were obvious but subtle motor planning and visual-spatial (relative?) weaknesses. Over time, he has improved tremendously. I think video games and instrumental music helped along with neurological maturation. At this point, he may even be above average in those abilities but still with certain subtle issues that are generally well-compensated. It is hard for me to judge visual-spatial because my abilities are far superior to his but then they also are to the average person's. I think his visual spatial skills are okay partly because he did extremely well even with AoPS 3D Geometry problems - he can visualize well enough to create and manipulate 3D images using software in order to solve problems. Of course, when he drew and extended 3D images by hand they look confusing.
