Indeed it doesn't. When one exchanges RMB for XBT on a Chinese exchange the transaction has no affect on the value of the Forex value of the RMB relative to any other forex currency. Bitcoin isn't traded in the forex at all.

When one exchanges RMB for XBT inside China, the total quantity of RMB doesn't change, only the ownership of that the RMB exhanged chages. If that XBT is then exchanged for USD on an exchanged in the U.S., then once again the total of USD in the USD doesn't change, only the ownership of the amount of USD exchanged does. There's no forex market effect either as no FX market activity occurred.

On the other hand, when one exchanges RMB for USD in order to effect a wire transfer of said USD to a destination outside China, the effect is quite different.

While the quantity of RMB may not change, the quantity of USDs held inside China has to decrease by the amount remitted abroad. This has an effect on the value of the RMB relative to the USD in the FX markets.

Bitcoin transactions have no such effect. Indeed they have no direct FX market effect at all, making bitcoin remittances a very good way for China to allow its population to