I think what the author means is that g is a statistical necessity, and that being such, doesn't imply that it's an actual reality.
What you seem to be saying is that, in any case, g is a useful proxy for a reality that is difficult to know in detail. This doesn't contradict the author's thesis.
The question remains, does g exist beyond arithmetics, is there such a thing as "general intelligence". Maybe it's a useless question, in that we don't need to know whether g "exists": we only need to know that it works.
But there is a big difference between intelligence and thermodynamics: policies are implemented that impact the lives of millions of people based on an understanding of g that may be completely false. If g is only a statistical artifact and nothing more, then it's still useful for statisticians, but for policy makers, the underlying factors need to be identified and understood.
That's why I object to the term "statistical myth" - it implies the measure is not useful in cases when it is. If g is a useful proxy, it's useful for policy makers. All they need to know is that low T implies dead homeless, and low g implies a higher probability of unskilled employment.
The fact that g is actually a sum of independent variables, or T is a sum of squares of velocities of particles is irrelevant to them.
What you seem to be saying is that, in any case, g is a useful proxy for a reality that is difficult to know in detail. This doesn't contradict the author's thesis.
The question remains, does g exist beyond arithmetics, is there such a thing as "general intelligence". Maybe it's a useless question, in that we don't need to know whether g "exists": we only need to know that it works.
But there is a big difference between intelligence and thermodynamics: policies are implemented that impact the lives of millions of people based on an understanding of g that may be completely false. If g is only a statistical artifact and nothing more, then it's still useful for statisticians, but for policy makers, the underlying factors need to be identified and understood.