I would add that on the WISC, for example, you can get qualifying DYS level IQ scores using VCI, PRI, or GAI, and not have those scores on FSIQ due to low working memory or processing speed, (attention deficits, LDs, etc.), and both PSI and WMI greatly influence how well you are able to perform on achievement testing. Since there are 2-E kids with DYS level IQ scores, it seems fairly straightforward that only a subset of those kids are also going to have DYS level achievement, particularly since diagnosing and getting appropriate accommodations for LDs in profoundly gifted kids is such a challenge.
