Fluid Reasoning has some overlap with visual ability, but mainly it is a measure of abstraction. His concrete visual-spatial skills appear good, as block design is not far off of his verbal comprehension subtest scores, in the Superior range. Visual working memory is good too (picture memory), in the Very Superior range. So it's not visual skills per se that appear to be the hang up. It's more like abstract reasoning, and even more, processing speed.
Yes, this is an unusual range of index scores, and would normally suggest that the Full Scale is not fully representative of his ability profile, though in his case, the strong block design and picture memory scores do help to balance the areas of relative weakness. The Full Scale doesn't require or include picture concepts or cancellation. It almost looks like the examiner tacked on two extra subtests -because- the indices appeared discrepant from the others--possibly in an attempt to see if the results were fluke-y, or maybe because they've had experiences with needing more data in those areas before. I can see completing the whole fluid reasoning index, as that and verbal comp are the best predictors of overall intelligence. The second processing speed subtest doesn't have an obvious justification, though, outside of probing for a discrepancy.
Sorry, wandered off into psychometric musings for a moment, there!
A relative weakness in fluid reasoning would certainly have many implications for social skills, as social perception and social reasoning are quite abstract, relying, as they do, heavily on perspective-taking. Weak fine motor speed (which is what may be behind the relatively lower processing speed scores) would certainly make sense with writing and gross motor/motor coordination issues.
Diagnosing learning disabilities at age 4 is a tricky business, but there is certainly enough here to keep a close eye on him. The kind of skills he might excel at at this age are still largely concrete (mainly what I would consider vocabulary activities--learning the language of various disciplines, whether that means actual reading, basic arithmetic facts/operations, or scientific/historical facts), and draw mostly on his excellent verbal skills. As academic reading and writing begin to require more inferential comprehension and analysis (not for a while yet!), this kind of profile, should it persist, might present more of a challenge.
However, at this age, cognitive development is still quite fluid, so it is not at all unreasonable that this might represent asynchronous development. Again, I would keep an eye on him, but not panic. Also, it may be worthwhile to anchor your perceptions of "hard time" against a good selection of typically-developing four-year-olds (if you can find any!). None of his scores are below normative, at the moment. I don't know what your situation is, but is it possible that his writing, social skills, and gross motor skills are actually within normal limits for late four-year-olds, but your perceptions are being dragged off by his advanced language and visual-spatial skills? Has he otherwise been assessed for these suspected areas of delay? At nearly five, you can absolutely take him to your local public school district's early childhood diagnostic center and ask them to take a look at him (request an evaluation for an IEP/IFSP), if you are seriously concerned. If you do, just make sure to bring your other testing results as well, so they don't re-test him with the exact same instrument (if it's close enough in time, they may ask to supplement with some of the other subtests, and combine the results).
So, in summary, the scores are unusual, they could be an indicator of a problem, or they could be not. If you're concerned, take him to the school district and request a special ed eligibility evaluation.
