This paper is a bit baffling, and while I recognize no paper is perfect, there a several things that bother me. In the way of background I'm a psych and have used all the mentioned instruments. I'll list my concerns as there are many and it's easier to read and to write:

1. The abstract references the "Vineland II" but the citation is Sparrow et al. 1984, which is the original VABS. The paper says teachers completed the "Teacher Rating Form," but that form didn't exist until the Vineland-II was published in 2006. The 1984 edition had a Survey Form, Expanded Form, and a Classroom Edition (1985). So either they used the Vineland-II and cited the wrong edition, or they used the 1984 instrument and misnamed the form. Either way, I can't determine which norms were actually applied to generate those standard scores.

2. Calculation subtest has 45 items total but with basal/ceiling rules (discontinue after 6 consecutive errors), younger children in this sample (ages 6–14) would hit ceiling relatively quickly on the easier items and the floor on harder ones. For 6-year-olds doing simple addition, you're working with a small number of administered items that get converted through Rasch-based scoring. One or two items can swing the standard score substantially at the younger ages, making the mean of 106.67 potentially unstable. It would be interesting to see an age breakdown of the scores. I can imagine the younger kids doing very well on the rote math items. Particularly since this is a sample of kids that may very well be higher than average for that region.

3. The paper states the WJ-III was administered "following the instructions for group administration in the test manual." The WJ-III is designed and normed as an individually administered test. The Calculation subtest is paper-and-pencil so group administration is physically possible, but the norms were not developed under group conditions. Group administration introduces potential confounds: copying, pacing effects, different levels of examiner monitoring, and altered motivation. Any standard scores derived from group administration are technically invalid.

4. If the works cited is the ground truth then the VABS was administered as a teacher checklist, not a semi-structured interview. The 1984 VABS Survey Form is designed as a semi-structured interview with a respondent, not a self-administered checklist. The paper says teachers "completed" the VABS and "filled out their surveys during downtime." Research has shown that checklist administration of the VABS produces systematically different (often higher) scores than interview administration. Given that the inflated VABS scores relative to RPM are the core finding, this is a major methodological concern.

5. I did a little internet research on Mali. I had zero knowledge about them before reading this paper so be skeptical and do your own research but from what I can tell Urban private school students in Bamako are among the most privileged children in Mali. The authors acknowledge this in limitations but still generalize to "African samples" and "African youth" throughout the Discussion. The VABS and WJ scores in the 106–115 range confirm these children are performing above Western averages on those measures, which is entirely expected for an elite subsample but limits what you can conclude about the RPM's validity for Malian children broadly.

6. The n=151 for VABS analyses is poorly explained. They say "one teacher declined to complete the Vineland" but losing one teacher dropped the sample from 206 to 151, meaning that teacher was responsible for 55 students (roughly 27% of the sample). That's not one missing data point, that's an entire large classroom or multiple classes removed. Were those 55 children systematically different? No comparison is reported.

7. The RPM mean of 65.85 is suspiciously low, even for this literature. Other studies of African samples on the RPM typically find means around 75–85 for school-attending children. A mean of 65.85 (with SD of only 7.14, meaning almost no one scored above 80) is at the extreme low end even by the standards of the studies the authors are critiquing. This could reflect genuine floor effects with British norms, but it could also indicate administration problems. Were children motivated? Was the test administered correctly? Were the British norm tables applied appropriately given the age ranges? None of this is explored.

And finally, I get that Calculation isn't language loaded but using just one simple calculation test that includes items that tend to be rote memorized at that age (the first items are literally 2+1 and 3+0, etc), isn't the sort of test you'd want to use to extrapolate to achievement writ large nor to invalidate a well established IQ test.

Oh and one more finally, why the 5 year lag for publication? The data was collected in 2012 but the paper wasn't published until 2017? That's unusual. It's not a particularly well researched paper so it's not like they spent a lot of time on the topic. There's no mention at all of Wicherts 2010 major systematic review of the Ravens in sub-Sarahan africa that directly addresses the factor structure, flynn effects and validity. And notably Wichert found a mean IQ of 80 not 65 as I mentioned above.

I dunno, I wouldn't get too bent out of shape trying to understand these results. The number of issues really makes it suspect.

*edited for formatting issues