I noticed that too, and I see it as something good since Japan has shown to be far more Bitcoin friendly than China has ever been/will be.
It doesn't matter anymore since Chinese trading has lost its shine. China was interesting for traders due to the zero trading fees, which allowed high frequency traders to demolish the market with their reckless gambling behaviour. Right now the western exchanges are making up the market direction and China just follows quietly. We can thank the PBOC for destroying something that needed to be destroyed a long time ago.
I started to realize that it was just a big show where people (me included) have been tricked into thinking Chinese exchanges were the most important aspect of Bitcoin trading. Reality turns out that they by far aren't what we thought they were. If you look at the top volumes after all this, then it's bitFlyer and Bitfinex that are leading when it comes to their volumes. I just wonder what made bitFlyer suddenly that popular as I didn't see that exchange pop up very often before the PBOC regulations.