The reasons for which is a matter of some debate, but the fact will resist any and all efforts to change it by way of insulting its speaker.
Were it someone relating this in a less analytical way, that sentence would read "People with higher IQs are not necessarily 'superior'". Which is also true, as it happens.
For anyone interested in the potential reasons: one of the most posited ones is that the creators of the tests are inherently biased. i.e. if someone creating an IQ test is a white male, chances are white males will have an advantage on the test.
This has some degree of experimental evidence behind it, I remember in one of my psych classes we learned about a study where test creators tried to create tests [and succeeded] where certain races or locales would score higher [primarily by having people in those places or people of that race create the tests]. It's very hard to create a "general intelligence" test that isn't biased in some fashion [and many say it's impossible]
But why and how would white males consistently create culturally biased tests which advantage East Asians?
> It's very hard to create a "general intelligence" test that isn't biased in some fashion [and many say it's impossible]
Tests of reaction time are probably not culturally biased: https://en.wikipedia.org/wiki/Mental_chronometry#Mental_chro...