Native Korean here, It's way worse here. It has been a decade since former telecom board members in the chief of Korea Communications Commission, which should prevent this in the first place.

The Netflix trial back in 2021 beforehand was due to SK Broadband (South Korean ISP) having lots of NTT bound traffic since they didn't join the Netflix's OpenConnect Program while requesting Netflix to co-locate in their server main content servers in (the SK Broadband). The results? Netflix found guilty for causing those traffics.

For your information, You can't establish an ISP in South Korea since the law forbids anyone other than "3 major telecom"s (SK Broadband, KT, LG U+). Regulations protecting telecoms and making sure CPs getting properly ripped off (Bonus point if you are not domestic business).