It's ultimately a selection bias for both. If you're in the top X percent to get accepted to Harvard Business School, you're also the type of person to have a higher chance of success in general. Same for YC.
The post is calling into question which network can best help a given candidate (who would have presumably been accepted by both) achieve their goals.
The post is calling into question which network can best help a given candidate (who would have presumably been accepted by both) achieve their goals.