I remember once reading that one of them (or some other FOSS alternative) was bad for privacy/FOSS, but I can't find that anymore

Not sure if you're thinking of WPS Office (formerly known as Kingsoft Office). It's development is funded by the Chinese government, but although Kingsoft claim that the Linux version is developed by the community, they haven't really published the source code anywhere, so it's considered a high-risk software.