Huobi's volume is simply too high to be real. They don't do any effort to hide their fake volume. It's simply ridiculous. Their 10 million BTC weekly volume is basically a milestone without being a milestone. It's fake.
All the Chinese exchanges compete with each other to fake the most volume so the winner can say it's the highest volume exchange. There's no way to find out the real volume on any of them, but it's minuscule compared to the faked volume. There's less than 15 million bitcoins in existence, and it's impossible that Houbi's got 70% of them.