The abstract mentions people with 170 average IQ. Hawking had 169 IIRC. Physics PhDs are averagely on the range 130~145. That's much lower than people on the study.

IQ is not taken seriously as a measure of intelligence or success anymore. And people can be trained to score high on IQ tests.

On the debate of Nature vs. Nurture, I do not think that inherent intelligence viz. good genes do not play a role. But I tend to belive that nurture has a larger to play.