Did she give you any indication regarding the subtests that comprise the FRI? One of them is untimed, while the other has time limits. If the untimed one is markedly higher, that would suggest that the index score is a likely underestimate.
I should also note that actually the behavior you are describing as typical of your DC is consistent with a young person who has relative challenges with cognitive shift, which would suggest that the index score--while possibly a low estimate of abstract thinking--may still reflect a genuine neurocognitive profile with regard to weaker adaptability. It's important to understand that the different dimensions represented by the index scores are interleaved among each other during administration, so that his very strong performance on both VSI subtests occurred on either side of one of the FRI subtests that the examiner describes as associated with fatigue and distress, which tends to support the idea that there is something authentically associated with the FRI tasks in particular that triggers this distress--not solely attributable to his overall perfectionism.
In short, you may be looking at a twice exceptionality of some sort, which further evaluation (or other aspects of evaluation that have not yet been reported) by your psych should help to elucidate.
