I'm not a score expert, but my DS had a roughly similar pattern, with PRI the highest area, followed by WMI. His overall VCI and PSI scores were similar to your son's, but sounds like a different picture when you look at the subtests.
Anyway, I don't think I would say that the PSI and WMI scores overinflate the FSIQ for your son. I'd say they show strong supporting skills. The precise PSI score is probably less meaningful than information from the tester on how he approached those subtests, but the score you have indicates that he's fast enough so that speed is not a concern. Good working memory (WMI) is good to have and can make it easier to do some things.
As far as PRI/VCI, what I see with high PRI is skill at discerning relationships and reasoning. But, I'm not sure how much of that is attributable to PRI and how much to VCI. My son's VCI subtests had a different pattern from your DS's, with enough variation so that the VCI is considered invalid, so I'd be reluctant to generalize too much.
What struck me was that your DS's vocabulary score was average while he has high scores elsewhere - I wonder if this reflects exposure? In any case, it can't hurt to make sure he is exposed to complex language and that you define words that might be unfamiliar.