2. a job doesn’t necessarily pay well just because it does require a high IQ. Scientists in a research lab, professorships, academic research all likely have more intelligent people on average yet don’t pay as well as software engineering.
3. The study still shows a routine and reliable difference in average IQ between those who work in manual jobs/trades and those who work in science/engineering
Software engineering in the US is well paid, yes, partially due to economic effects and impact of software in and of itself, but it is, especially in FAANG, a profession with a very high concentration of people near the higher end of normal and above in the IQ spectrum, which leads to implicit selection criteria regarding intellectual capacities in employment.