As someone who does research in this area, broadly defined, I think you're on to something, but I also think there are some misleading things about this article (which I nevertheless think is interesting) and caveats to what you're saying.
Lots of thoughts:
1. Intelligence is a broad construct. It is by definition, and it is not the only cognitive construct. It does have a lot of utility for certain purposes though, such as in identifying pervasive neurological disease.
As others are noting, this is relevant to the article in that we tend to focus on extremes when making these kinds of comparisons, when the full spectrum is really what's important sometimes. We tend to fixate on whether someone went to some prestigious university or less prestigious university, or whether our incomes are in the upper middle class or upper class, but in the sense of outcomes, compared to all outcomes, these can be relatively minor distinctions and hard to predict.
2. There are other variables that are relevant, like conscientiousness, ruthlessness, and so forth. This is certainly true.
3. There are still other variables that have nothing to do with the individuals involved though. The elephant in the room are societal and other random factors that prevent any individual attribute from mattering as much as they could. The article starts out by dismissing prediction among females out of hand because of societal limitations, which is reasonable. But there are lots of other variables involved, random and nonrandom societal and environmental forces at play. The hidden story is that there are limits to predicting outcomes at all from the individual at hand, meaning that other variables in the environment are working.
4. Measurement of intelligence is fuzzy and imperfect as you're alluding to. It's stochastically imprecise, in the sense that giving the same test twice, or two different tests, will give you somewhat different answers. But it's also imperfect in that the thing it's measuring isn't really what we probably want to measure in an ideal case. Even if the tests were giving the same answer all the time, it wouldn't really be intelligence in the way we want to talk about intelligence.
5. I'm not sure that we really want cognitive functioning measures to be perfectly stable, because I don't think cognitive functioning is actually perfectly stable. It probably varies across the day, for example.
6. Physical measurements are certainly more precise. But the objects systemically are much less complex. It's easier to talk about measuring the mass of a cubic meter of oxygen than it is to talk about measuring climatological variables; something analogous is in play with things like intelligence.
Also, even physical measurements at a certain level become fuzzy and highly interdependent. Measuring mass "precisely" depends on your scale and other variables.