I did a search to try to figure out if #Region0 discs where common/expected for South #Korean #DVD releases, and found this article which I was pleasantly surprised to see having been published in the Washington Post 22 years ago.

Breaking Down DVD Borders - The Washington Post http://web.archive.org/web/20170827102137/https://www.washingtonpost.com/web/20170827102137/https://www.washingtonpost.com/archive/business/2001/06/01/breaking-down-dvd-borders/dad3d4dd-ed1a-48b8-afa9-6418872db34e/?utm_term=.f9164a2c49dc