I tend to agree that you didn't learn anything particularly new about his learning profile. OTOH, I can understand why they recommended a small special classroom for him. Whether that is the best possible placement for him is a separate matter.
It strikes me that, though the swivel chairs probably didn't help, he probably would have been difficult to test even in an ideally-situated small, child-scaled testing room, as the precipitating factor for his first bout of noncompliance was a transition, not the room or its distractions. Several of the other behaviors reported by the behavior analyst were also associated with transitions. That he responds substantially better to you suggests that your familiarity with each other is extremely important to his ability to cope with change. (And as to the later outburst over being marked incorrect--this is why I never let children see my side of the testing materials, nor do I give anything other than accuracy-neutral comments on their performance.)
Obviously, from an academic standpoint, he will learn more at home with you. He will probably learn more cognitively in terms of pragmatics and social skills, too, though you will have to be intentional about creating graded alterations in his social and other environments, so that he has opportunities to generalize and apply those skills successfully. I suspect that generalization and transfer will not come without planning.
In the small classroom, he will have more opportunities for generalizing social skills in a facilitated setting (properly trained special ed teachers can cue and help process social interactions in real time). On the downside, his social partners will probably be more impaired than the ones you would find in your homeschool and community setting, and academics would be likely to take a back seat.
I would not worry too much about the loss of the pragmatics and social skills training as pull-out services, as those skills do not transfer well from in vitro to in vivo, anyway; he is better off practicing what he does know with real children, in naturalistic settings, but with on-the-spot coaching by adults.
