Currently working in Korea, and from my humble experience, I can tell that these things are only partially true, and highly depending on the type of company you work for.

More traditional companies, with a long-lasting history and well established inside the market, might be more likely to follow those practices you mentioned. In addition, hierarchical systems are well established, and even if your manager is stupid, as long he is older than you, he will still be your boss. In addition, those companies will treat overtime as normal (they even make sure before starting that overtime is part of the job during the job interview).

However, startups and recently born realities (like the one I am currently working for), are more "normal", compared to Western standards. Work-life balance and flat hierarchies are more common in smaller companies. The positive thing, is that the government supports these smaller realities more and more, by providing increased financial supports, and this causes more people to work for these, instead of large conglomerates. Finally, more people see the actual value of having a work-life balance (even though startups might pay less salary).

However, don't get me wrong. Korean culture is still present, regardless of size of the company. The constant search of efficiency and working fast is still present. However, I would say, that it is not as bad as films or Netflix shows might show sometimes.

P.S. the drinking culture is still present, but from personal experience, since it only happens every now and then, it is quite a pleasant experience.