The fact that any dimension reduction strategy from [super large and complicated space that is your brain] to [positive integer within a range] is badly calibrated should be news to precisely no one.

I don't think I agree with "badly calibrated," there. It's not like everyone saw g coming, or it doesn't see any opposition; it's surprising and interesting how much of the variance in human intelligence can be captured by a single dimension. Is it 100%? Of course not, and I say that because we calculate g loadings and correlations and have a good idea of just how much information g does or does not give us.