You can legally own dollars. You can legally obtain dollars in exchange for goods and services. You don't need to buy dollars with bitcoin. That's how money is supposed to work.
The key point is that this is tied to goods shipments. China encourages exports, and isn't that hostile to imports. Those are OK. Pure money transactions are subject to capital controls. Part of the purpose of this is to favor doing real business in goods over pure financial transactions.
Still not getting your point. China gov't doesn't recognize bitcoin as a currency, they recognize it as property, aka collectibles, aka "goods". So you should be able to "buy" them with Yuan any way you wish.