I disagree. The focus of discussion is on what difference an event - imperialism - made on the trajectory of african history, not on the average intelligence of Africans.
I suppose one could argue that the average intelligence of a group is the important determinant of every historical “what-if” scenario, but the absurdity of constantly harping on this must surely be evident. It reduces what is different about different questions on Africa to a boring sameness - simply put, every discussion on African historical questions would reduce to the same-old, same-old wearisome discussion about the Bell Curve.
Imagine if some group responded to every question like “What if Bismark’s unification of Germany had not happened?” or “what if the German generals had succeeded in assassinating Hitler?” with endless repetition of theories about the inherent intelligence of Germans. It would get annoying, fast.