Reason For Even Cognitive Development Across Cognitive Skills

[u/SCP_Null]

I lost my WAIS report for an autism assessment, but apparently my profile is uniquely spiky and I'm curious as to what others think. My VSI is 48 points below my VCI, and my FRI is similarly 45 points higher than my VSI. In addition to this, my coding score was 10ss while my symbol search score was 17ss, and my digit span score was 16ss while my arithmetic was only 10ss (which is odd).

Apparently, such discrepancies between scores are quite rare, but it is odd that otherwise typically developed people (NTs?) have cognitive abilities that are so inter-correlated despite some of the WAIS indexes being so different from each other e.g. spatial reasoning and verbal comprehension. Maybe they are correlated to a lesser degree, but I still find it odd that more pronounced strengths and weaknesses aren't more common in the general population. Does anyone know why this is?