I'm not generally interested in comparing IQ results between countries or even for people of differing first language though so these don't especially concern me so long as I can be sure a study averts the issue.
My point is the variability between test groups calls into question the reliability of IQ as a concept as a whole. If IQ is an innate measurement of intellect for humans in general, then the reliability of the test shouldn't be culturally constrained.
for instance, it correlates well with success (level of education (eventually) reached, or $ in a capitalist society) and I'd be surprised to find any major journal publishing a paper which disputes that.
Yes, but I could make the same claim about a plethora of other correlations with more confidence like having wealthy parents.