Or because Google did move out of mainland China and stopped censoring searches in 2010.
Yes, Google+ is the intermediate step in the all seeing "identity" service depicted in this story ;)
(Which is to say: Doctorow seems to have seen being in China as a big step on the way to relaxing "Don't be evil". But perhaps Google was only in China because it had already relaxed on "Don't be evil". And thus staying in China, or even going there initially, was relatively irrelevant to its corporate trajectory.)