"race" and "IQ" are fictions, so what does that do for their truth value?

I would ask, are these concepts truly useful?

I wouldn't say they're fictions anymore than I would say gravity is fiction. They're models, so by definition they don't fully encompass that which they're meant to represent. I think IQ has some usefulness, e.g. https://en.wikipedia.org/wiki/Intelligence_quotient#Job_perf... Race, well maybe, the political climate is usually too hot to entertain a rational discussion of that.