I don't think Ron's description, quoted above, is correct, for the most part. I don't even think it's true that there's disagreement about what makes a Verbal question challenging - if it were true that most questions were somehow roughly equally challenging across the difficulty spectrum (and therefore that most potential SC/CR/RC questions turned out to be unusable on the test), they'd need to include a ton of experimental Verbal questions on each test, to weed out the large proportion of unusable questions. But they've never needed to include a lot more experimental Verbal questions than experimental Quant questions.
What does seem almost certain to be true is that the highest possible difficulty level a Verbal question could have is lower than the highest possible difficulty level a Quant question could have. It's possible to design GMAT-format Quant questions that almost no test taker could answer (without a lucky guess). I don't see how that could be possible in Verbal. So that fact alone means
near the top of the scoring scale there will be a greater correlation between 'hit rate' and scaled score in Verbal. But you wouldn't observe that correlation at lower scoring levels, where the test is able to deliver questions both above and below a test taker's level (i.e. at ranges where getting hard questions wrong doesn't hurt you, because the questions are above your level).
And it's also true that the high end of the Verbal scoring scale just has no analog on the Quant scale. In percentile terms, a V40 is like a Q50 roughly. So if you're talking about hit rate in each section, and about how hit rate correlates to Verbal scores in roughly the V40+ range, then to draw a comparison with Quant you'd need to talk about hit rate and Quant scores in the Q50+ range. But there is only one Quant score beyond Q50, whereas there are lots of Verbal scores above Q40. If the Quant scale were capable of differentiating among people at the 97th, 98th, 99th and deep into the 99th percentile, as the Verbal scale does, you'd see a far greater correlation between hit rate and score in the Quant section too
at the top end of the scoring scale. You wouldn't see that correlation at all in the middle of the scale, though.
So I wouldn't say the Verbal section is less adaptive than the Quant section at all, if you're talking about the low and middle ends of the spectrum. It's only when you get to the harder questions that it's not able to adapt as successfully, because it's just not possible to create Verbal questions that are as hard as the hardest Quant questions.