Welcome!
As he is just into the age where IQ scores start to stabilize, and (I assume) this was his first formal testing experience, there may be factors other than his pure cognition that affected his formal test scores. That being said, it is possible to be GT and to have a profile such as this.
The best measure of overall ability in most persons is the FSIQ, which is in the GT range in this case. At the Index level, it appears that your DC is strongest in visual spatial thinking, with verbal reasoning and short-term memory not far behind (the WMI would not be considered significantly lower than either his overall performance or the other index scores). As you note, the PSI is very much in the range often recorded for GT children. The real outlier is certainly the FRI--which, remember, is not remotely below average, just below his other strengths. Assuming that this is a real result, my experience with this sort of profile in the past has been that in some cases, similar learners are less adept at cognitive shift, or flexibility in thinking, problem solving, and adapting strategies. That's where the "fluid" in Fluid Reasoning comes in. Another thought is that the profile sometimes reflects a more linear-sequential thinking style, rather than a lateral-simultaneous-associative style. It's hard to say with more clarity based only on the cognitive index scores.
With respect to your specific DC, if you feel comfortable providing a bit of a fuller picture, perhaps the community can offer some other ideas more tailored to your situation. What was the stimulus for seeking out evaluation? What kinds of IRL strengths and challenges do you see? What's an example of his abstract thinking strengths?
