This exact same balloon type was spotted floating over Japan in 2020 and India in 2022, https://twitter.com/BalloonSciDan/status/1479218147098038278 Plenty of companies are working on airships including in China. Companies building airships of similar scale: https://aviationoutlook.com/airship-manufacturers/ The US puts hundreds of balloons over China, https://www.weather.gov/jetstream/radiosondes
"Worldwide, there are about 1,300 upper-air stations. Observations are made by the NWS at 92 stations - 69 in the conterminous United States, 13 in Alaska, nine in the Pacific, and one in Puerto Rico.
NWS supports the operation of 10 other stations in the Caribbean. Through international agreements data are exchanged between countries worldwide."
This seems to suggest that NWS does not operate those over China but the map simply shows all the balloon weather stations that are part of this system.