I agree, this is about intellectual and spiritual achievement, not just being ehrliche or shomer shabbos.
There are similar observations in other intellectual areas that may or may not transfer to Learning:
– regression to the mean. Every exceptionally gifted person passes his genes to kids but chances that they’ll be as or more gifted are slim. Starting that he will probably marry someone not in the same category and just basic stats
– exceptional intellectuals are not always good at chinuch and teaching kids alef-beis. I observed this among chess players and scientists: solid professionals invest at teaching their kids their skill and kids may reach same or higher level; those at the top spend 100% time on their own achievement and their kids are either abandoned or intimidated.