Mean for sure but between the 15yo in question being a woman in a college environment and this only happening in front of 1/10th of 1/4th of the undergraduate student body I doubt it was of any practical hindrance.
Rushing through undergrad is possible if you do nothing but grind homework and study and read.
Grad school requires you to spend hours and hours in a lab, ass-in-seat, doing research. You're no longer competing with beer pong champions. Unless you're an absolute genius at finding the right direction to solving a novel problem, you're not going to get dramatically better results than your peers. And even if you are, you might be unlucky, and end up wasting a lot of time going down the wrong rabbit-hole.
EDIT: Almost forgot: I did skip a year during elementary, not sure about her case.