Watching "Through the Worm Hole" I was suprised that they seriously discussed genetic influences on IQ. Races are advantaged in different ways and dis-advantaged in others. However I don't believe that two people of the same genetic background with high IQs tend to give birth to high IQ children. In fact, statistically there should be a regression to the norm meaning the child is more likely to be less intelligent than either parent.
You are quite correct.
However, the group of children born to two high-intelligence parents will be considerably more intelligent than the group of children born to two low-intelligence parents. Which is the statistical point here.
If you breed the two fastest horses in the world, their offspring is likely to not be as fast as either parent. But the colt is still likely to be much faster than the average horse.