I don't see why it's surprising: IQ is one of the few tools that modern scientific racists have in their toolbox. One wouldn't expect them to let such trifling concerns as "evidence" and "testable models with successful predictions" take that away from them.
There is such a thing as general intelligence which differs between different people. Arguing that IQ isn't real because IQ tests are imperfect, is like arguing in the year 1500 that temperature isn't real because all thermometers are imperfect.
Our lack of ability to precisely measure something does not mean the underlying thing is not real. There is such a thing as general intelligence which correlates strongly with almost every type of performance and life outcomes.