Chinese started WPS Office (called Kingsoft before) in 1989. Since end of 90s it is state favored and in 2011 received major grand. My wild guess is that they have much more incentive to use this rather than some broken open source Java thingie which is generally much slower than WPS.
This package is 36 years old and very often overlooked by analysts dunno why. At time of writing there isn’t a single mention of this in the comments… very weird?!
https://en.m.wikipedia.org/wiki/Kylin_(operating_system)
Unsure what office tools they use though