It’s not so much a case of circular reasoning as it is a matter of definition: intelligence is defined as whatever it is that IQ tests measure. But, (in the article) you can see that there are a bunch of things that correlate (and that anti-correlate) with IQ, that seem not directly related to whatever it is that IQ tests measure.
I thought it was said that IQ is defined as whatever it is that IQ tests measure. Intelligence is a concept temporally and logically prior to the IQ test.