NVLD is the subject of ongoing discussion in the field, so you will hear different views on what constitutes NVLD, or even if it exists, from different professionals (it is not a DSM-V diagnosis; closest related Dx is probably SLD in mathematics). For those who find the data to be supportive of its existence, the most convincing descriptions of the profile I've seen emphasize the perceptual-visual-spatial deficits (social skills deficits are actually secondary effects).
The intent of the WISC-V FRI is to assess abstract thinking and problem-solving, as distinct from verbal reasoning or spatial reasoning. Of course, one must use some means of accessing the items, and the need to reduce language effects results in more visually-oriented tasks in the FRI, but they're not as strongly reliant on perceptual or spatial thinking as the visual spatial tasks are (partly because they are accessible to using either visual or verbal reasoning to solve). On the WISC-IV, the FRI-type and VSI-type subtests were combined into the PRI, which means that some children, who had high FRI-type scores, but low VSI-type scores, didn't show a difference between VCI and PRI at the index level. A reasonable fraction of clinicians noted and reported the differences anyway, at the subtest level, but a pretty sizable proportion did not, leading to underidentification of NVLD. Hence the improved identification of NVLD on the WISC-V.
In the past, I have sometimes selected the DAS/DAS-II to address this confound of visual spatial with fluid reasoning, as the two areas have been separate on that instrument from the beginning. It also can be picked up, for some children, on the SBV (not as well, because of the paired verbal/nonverbal structure of each area), or if enough additional subtests of the WJ are given.
Of course, some persons who could be described as NVLD have deficits in both visual spatial and fluid reasoning. They were easily identified on the WISC-IV, and continue to be readily identified on the WISC-V.
There's a decent description of NVLD, and its distinctions from ASD, in this little article/book excerpt. Note that the end of the comparison chart is off by two rows, beginning from the section headed "Behavior" (you'll see the two extra rows of "mostly" or "sometimes" at the end--back them up two rows, and they will be lined up again):
http://www.nldline.com/yvonna.htmI didn't vet it in its entirety, so I can't vouch for 100% accuracy, but the gist of it is reasonable.
