Trading relies on centralised platforms.  By regulating Bitcoin exchanges, what they're really doing is pressuring websites to abide by specific regulations (or to close down) - this is easy, because it's just a website, not a decentralised network.

Mining, on the other hand, is decentralised.  By "banning" mining, they would be banning something which could happen in any home anywhere without their knowledge, so it would be a very ineffective law.

Also, since electricity is cheap there, it's actually beneficial for the Chinese economy as a lot of miners make significant profits from it there.

By attempting to ban mining, they would be basically banning people from making a potentially profitable investment, and not even succeeding in doing that.  So it seems very unlikely that they would ban mining.