A few years ago (2015?), UC Irvine had 800 more students accept admissions offers than expected. UCI didn’t have room to accommodate them. In late June (!) 500 of those students received letters rescinding their admissions offers.
Ethical? Or just a case of doing what had to be done under extraordinary circumstances? Somehow the University of California found a way to justify that despite what appeared to be an ironclad offer of admission.
It’s a 2-way street.