rr, I'm sorry you're experiencing such frustration with your DC's school. I would agree that he probably does not need additional OG for decoding, with such strong scores. However, he does need practice and overlearning to reach fluency. Whether or not the school wishes to address fluency, there are some good resesarch-based (and inexpensive) options available. I would suggest taking a look at HELPS (
http://www.helpsprogram.org/materials.php), which is available as a free download (or inexpensive binder), and is easy enough for an organized and responsible college student (or parent) to implement in a fairly brief daily tutoring session (3x/week would probably do it, too).
BTW, his much lower reading comprehension score is very likely a reflection of fluency/automaticity deficits in reading. As I referenced above, he is likely using most of his reasoning energy on decoding (which is an achievement he should be proud of, but doesn't leave enough for actually understanding the passage). Attempting to remediate comprehension without addressing fluency is in some ways putting the cart before the horse. If he could read it easily, he would probably understand it.
I agree with your psych; I often find this profile of historical test scores in my dyslexic secondary students. If this didn't happen already, I'd ask the psych if there is value in administering the other two supplementary verbal subtests, and calculating a VECI (Verbal Expanded Crystallized Index), to try to capture a little additional verbal reasoning through skills with less of an academic basis (such as the Comprehension subtest). Not unusually, I see 2e learners of this general category with high verbal reasoning scores (Similarities, Comprehension), but lowered verbal knowledge scores (Vocabulary, Information), in which case I believe that the clinical interpretations of verbal reasoning and verbal knowledge are better represented separately.
