A very small fraction of the population earns a living through sports or music, but for many people, the level they reach in the occupational hierarchy is limited by IQ, so of course parents are more sensitive to even indirect information about the IQ of other children.
I really do not think this is true, nor do I believe most parents are sensitive to this. And, it very well could by a sport or fine art that becomes a child's passion that drives their academic success later. That is important, too. And, a child with a higher IQ could be lacking this.
I think that if one believes that the higher the IQ of a child the more successful in life they will be (i.e. their occupation,) then I bet that comes across in the way one interacts with other parents. Maybe they are sensitive to that.
