"Chinese friends/wife/coworker said" is particularly kind of ridiculous appeal to authority considering the average citizen is not typically a subject matter expert on relevant topics being discussed outside of generalized familiarity with the censorship apparatus. The only useful things the average Chinese person will tell you is Chinese numbers / stats with Chinese characteristics are not accurate, but analysts familiar with Chinese stats will at least use oblique indicators to tell you if numbers are useful, i.e. Chinese GDP smoothing.

Or in this case, how covid19 export case numbers from places like Taiwan, HK, SK, Singapore, Australia, Newzealand all indicate Chinese numbers are not grossly exaggerated - China only exported a fraction of covid19 cases compared to Europe or North America because covid19 never exploded in China due to harsh restrictions. The article you're citing is also sourcing figures from _Chinese_ CDC on antibody prevalence rate which is expected to be higher than pure testing data seen in similar studies in other countries. So again, it's official Chinese numbers being useful and comporting to similar measures elsewhere. The difference is western media like BBC attempting to spin as the numbers being uniquely nefarious and useful idiots eating it up, just like in this NYT article.