It depends: if their goal is to export capitals, when they get foreign currency by selling the BTC they bought in China, they will keep that currency abroad and

It depends: if their goal is to export capitals, when they get foreign currency by selling the BTC they bought in China, they will keep that currency abroad and invest it there. Of course you can do the same with mining - instead of buying BTC at exchanges - but this will require first investing in China to buy China built mining equipment and operate your mine. That's the difference I see.