Another thing I've noticed is that many of the super high SB-5 numbers come from age 5. Could be a mere coincidence, but perhaps not. I'm not saying at all that your son isn't actually super high, only sharing observations.
That's an interesting finding, and I guess not surprising. Perhaps their norms for five year olds are not as reliable. I'm sure he's very very bright, I just found the discrepancy between my view of him and the way other kids on the board are described to be surprising. I agree with the other poster about the issues with vision/coordination, etc. He is in therapy, so hopefully those things will improve...