Before Suneung, there were equally, if not more, grueling college entrance exams. I think the point the commentor is trying to make is that this type of education has been the fuel for Korea's social and economic rise.
And note, historically, that under earlier Korean dynasties from 958 CE Korean elites like their counterparts in China vied for official posts through a grueling set of state exams, collectively known as the "gwageo". The median age of passing the final phase was around 35 years in age, and with a very low rate of passing (14600 passers between 1393-1894, among many millions of aspirants over the centuries) this effectively meant that most members of the elite class spent long decades mastering the complex Confucian canon and wide range of poetic forms required for success. Some passers were in their 70s.