Would it be easier or harder for the average person to reach the bar of 'average software engineer', since 'average person' is a less-selective barrier. Your selectivity theory yields the unintuitive result that it's actually easier to meet the bar of 'adequate for average software engineer' when starting from general population than starting from a selective group of software-engineer material. Or maybe, just maybe, it's possible to hold every cohort to an objective standard.
Harder than what? Harder then a smarter person? Then Yes.
I also wouldn't call it a "selectivity theory." It's more common sense. You select a group of people with a record of great past performance they are more likely going to have an easier time. It's actually your ideas about selectivity are counter-intuitive.
