Because of Canada's immigration policy, most of the immigrants are highly educated, they wouldn't be an immigrant if they didn't finish high school. Refugees is everyone else who couldn't immigrate and had to go the other route.
So you might have a Sudanese immigrants who are highly educated and Sudanese refugees who are more likely to be illiterate (a bit generalizing but still).
This is very different from US where you have a green card lottery and your typical immigrant is just an average population because everyone has the same chance of winning lottery, it doesn't matter if you are a farmer or aircraft engineer.
He mentioned IQ and industriousness, not level of education. There is only a weak correlation. (And you are not likely to successfully make it from Sudan to Canada if you are lazy and stupid.)
Educational attainment is correlated with lots things. For example, there is a strong correlation between your parents' wealth and your educational attainment. Your argument would make sense if IQ were the only thing correlated with educational attainment, but it isn't.
This is very different from US where you have a green card lottery and your typical immigrant is just an average population because everyone has the same chance of winning lottery, it doesn't matter if you are a farmer or aircraft engineer.