The Cat. III films that we all love and adore were made prior to the Chinese takeover in 1997 and thus were made when HK was a British colony.
According to some Cat. III fans, films originate from the country that owns the country where they were made. It is thus only a logical argument that pre-97 films must be regarded as being British.
So thank-you's go out to the UK for giving us EBOLA SYNDROME etc. You British film-makers are thee best!
But seriously ... HK isn't in China. It's a territory with its own flag, currency, language (Canto Chinese), government, laws, left side of the road driving (right side in China), film regulations, etc. that is governed by China.
China doesn't have a censorship board that classifies films into categories. Category 1-3 are strictly for Hong Kong. In fact China doesn't even HAVE a film classification system. They may ban films, cut films, "disappear" the director, but classify films, no.