No, ethnicities are absolutely not just administrative or cultural groupings. You've clearly done no research into this topic whatsoever and are just repeating some misinformation you got fooled by. Even the classic races which are unnecessarily crude by modern standards do actually partly correspond to distinct genetic groups. We can now classify ethnicities at a much finer level of detail and they're still distinct genetic groups.
Ironically given the article this is under, IQ was considered to be dirty Jewish science by the Nazis, probably because it showed Jews to be superior.
Honestly, you just sound like you're a racist. Which is sad, but it's also indicative of a lack of common sense that you expect the universe to conform to your prejudices.
You must also think scientists don't believe in the distinction between planets and dwarf planets, or even stars. Yes it's an arbitrary classification, but it's still useful.
You're thinking is just like the people in TFA. Rejecting some science for arbitrary and nonsensical political reasons. You've replaces dirty Jewish science with dirty racist's science.
> The genetic variation across one race (say black) is much greater than the variation between races.
Why did you say that? Are you implying that there must be a wider range of IQs among various ethnicities within a race than between races? That's not a logical conclusion. Do you have some other chain of logic in mind?
By the way, I only use the word race loosely. I really mean ethnicity. Although the findings do still broadly apply to the classic 3-ish races.