No nonstops between Europe and Japan---politically, that wouldn't fly too well in Japan anyway! Air China flights between Japan and Europe will all stop off in the mainland, mostly in their PEK hub. The wording on the luggage applies to these connecting itineraries as long as they are on CA.

CA isn't stupid. By coming up with a policy that offers Japanese customers an increased baggage allowance via the piece system, at a competitively- priced ticket, it encourages them to give serious consideration to a somewhat more inconvenient journey via middleman China when en-route to Europe. Which is a routing in which Japanese travelers are likely to want to be doing some serious shopping in Europe and thus mostly bringing lots of stuff back. At least it makes these customers weigh the option rather than automatically default to the nonstop routes on Japanese- or European-based carriers. And of course, this works in the opposite direction for Europe-based flyers heading for Japan.