Well if they have overcrowded the mining environment that does not allow the smaller outfits to compete for the amount of coins available to mine. Then yes they are controlling how much is available across the board. Essentially hording all the available power to mine those coins available.
It's not only the mining power that they are ruling, but also the trading volumes. I know that their volumes shouldn't be taken too serious as large traders can easily buy and sell into their own walls, but it's very impressive none the less. Chinese people like to invest their money into Bitcoin as it nurses their speculative way of investing.