This explains why there aren't external forces that can check the growth in credit.

But there has been an explosion in debt within China, financing ultimately non-productive investment. Even with a positive external debt outlook, you can get wild economic imbalances within a country via uncontrolled credit creation. The hangover could be profound.

To put it another way: why do you think centrally-planned economies are frequently outpaced by capitalist economies? Misallocation of resources. Debt binges are similarly distorting.