Your DC's cognitive scores don't have to be 18s or 19s to mean GT. Index scores above 130 are the standard threshold for GT, although I will say that visual spatial giftedness is probably the least appreciated and most misunderstood, especially in elementary school, where the focus of academics is very much on language (even the math is essentially language, as it's mostly the grammar of arithmetic, rather than higher-level reasoning and problem-solving). If you've been lurking here for a bit, you may have heard me say that this kind of profile often doesn't come into its own academically until much later, in high school or even after.
His other index scores are 20-46 points (1.3 to 3 SDs) lower than his VS strength, which is entirely consistent with a 2e profile, even if you qualify the Symbol Search score as a likely low estimate. (Though I tend to view all behavior as meaningful. There are obvious interpretations of the low SS score, and then there are other interpretations. In particular, very bright individuals not uncommonly mask deficits with behavior; IOW, "I'd rather look like defiant, like I choose not to or don't care, than look incapable.") You're still looking at about a 2 SD difference between strength area and nearly all other areas. I bet if they had done Arithmetic too, to obtain a Quantitative Reasoning Index, they would have found a strength in mathematical thinking, as well (based on the Figure Weights score and your anecdotal reports of his current mental math skills). One hopes Belin-Blank will do so.
Nor does every GT learner have noticeable or disruptive OEs. (That's actually still a somewhat controversial area of GT studies, inconsistently supported by the data.) And many here have realized, on reflection, that "extraordinary" is very much context-dependent, by definition. In certain communities, I expect you would have most certainly been considered extraordinary. And at a PG gathering, some of the exceptionally bright learners attached to this forum wouldn't be considered extraordinary.
Perhaps, consider yourself blessed not to have had many of the issues that accompany the GT experience for others. (As an analogy, just because it's developmentally-expected for adolescents to have a certain level of conflict with their parental figures over autonomy doesn't mean that a parent-child relationship that navigates adolescence with affection, grace, and mutual understanding is somehow flawed!)
Returning to your DC: his VCI was average, but you appear to have reports and observations about his vocabulary which are discrepant. It is possible that this is simply another example of small-child-inconsistent-testability, but his intra-Index scores are so consistent that I'm not sure I can fully buy that. I wonder a bit if there might be something else, perhaps a subtle expressive language delay (despite meeting some early language milestones), even beyond the difference between language and visual spatial thinking skills documented in the existing testing, as often the behaviors you describe are a response to a gap between thinking and communication skills (this is, of course, a big part of why NT and GT toddlers alike are known to throw tantrums). I would hope that Belin-Blank includes speech and language testing in their evaluation. Even with excellent or advanced vocabulary skills, there is a huge difference between being able to accurately use vocabulary in context, and being able to summon the expressive language to define vocabulary in isolation.
