Actually, that's my point. They were accepted and told that their product was no good straight away, thus forcing them to pivot. So why were they accepted with a poor product, when other applicants who had stronger ideas were turned away?

A selection process that supposedly values the skills of the people over the combination of skills and product will lead to people like this guy not knowing why they were selected, and not being able to handle pivoting. It's something YC should stop doing before it causes real damage.