The Paracel Islands and Spratly Islands in South China Sea don’t belong to China. Politically, it’s being sovereignty disputed between many country. Historically, it belongs to Viet Nam (during the time VN is still France’s colony and VN war, even before that). China has been illegally doing military actions in those islands. Please fix the information shown in OSM. Thank you.
https://m.imgur.com/a/F58WTmc
Maybe this document will help you:
https://wiki.osmfoundation.org/w/images/d/d8/DisputedTerritoriesInformation.pdf
Main takeaway being that OSM maps things as they are on the ground (de facto), not necessarily the legal status (de jure).