> Suppose you’re hiring someone for a job that requires a few different mental tasks. (Arithmetic, sequential memory, whatever.) If you knew someone’s g, you could guess how well they’d do at each task. But it would only be a guess! To really know, you still need to test the skills individually.

I think this part in the conclusion somewhat contradicts a lot of the analysis. In fact, the results have shown that if you knew someone's g, your guess at their performance on each task would be a good guess.