If this is true, then I am curious what precise definition of “IQ” the people who develop these tests and scoring scales think they are using.
I was taught that it was an ordinal ranking that is wrassled down and converted at gun-point to a normal distribution (mean = 100, sigma = 15/16), but if what you are saying is right then this must be incorrect or perhaps (as I suspect) it’s simply that these testing scales are not well calibrated in the tails.
(The archaic definition as “mental age / physical age” could give non-normal distributions, but this was never made rigorous and is at least 70 years out of date.)