Given that he's "accusing" his own race of being less physically capable I can only assume that the same goes for other traits in other races. Have a look at who has been winning long distance running events for the last few decades and you'll quickly find out that people from a certain area - nay, a certain tribe [1] - in Kenya are grossly overrepresented. This is not because they're all using doping like e.g. athletes from the former DDR did, it is because they share a mixture of genes and culture which makes them exceed in this field. Going by the data it seems clear that people from certain areas in the world - mostly in Asia and Europe - share a mixture of genes and culture which makes them exceed in what you call "strenuous intellectual activities" [2].

You seem to be upset over his pointing out this fact. Why is it no problem to point out that these Kenyans are dominating long distance running - even NPR reports about this - but problematic [3] to point out that the Japanese, Swiss, Chinese, Americans and Dutch dominate when it comes to intellectual pursuits? I suspect this is because intellectual pursuits have a higher standing among the "educated" classes who tend to ruminate about these things than physical activities. In a way this itself is problematic just like the way many "educated" people look down upon physical labour is problematic - to use a term often bandied about by those same people. A healthy society needs both those who are more into physical activities as well as those who are more into intellectual pursuits to develop and thrive - this is true diversity.

[1] https://www.npr.org/sections/parallels/2013/11/01/241895965/...

[2] https://www.forbes.com/sites/duncanmadden/2019/01/11/ranked-...

[3] https://newdiscourses.com/tftw-problematics/