penley
In my experience, more often than not, "tough love" becomes conflated with toxicity, which causes people to start avoiding crucial conversations in order to avoid the perceived toxicity. Important feedback can become stifled by our desire to maintain a congenial and friendly atmosphere. We forget that some of the toughest times come when we're suddenly blindsided by a situation that's been brewing for months or years, that we were blissfully unaware of. Our first indication of a problem is being passed over for a promotion, or not receiving a return letter.
This is an unfair situation for all involved parties. Honest feedback during the internship may have given the author a chance to adjust course, instead of being (justifiably) dismayed by a surprise result. By allowing this communication failure to occur, and not granting the courtesy of clear feedback, the leader in question damaged a relationship with a talented engineer, someone who may end up working for a competitor, or even starting a competing startup.