Why do you assume Google wouldn't be affected by a Windows bug? Have you forgotten about the compromise of their corp networks by a Chinese APT in 2008/9 which leveraged Windows as the attack surface? The reason for disclosures like this to expedite bug fixes is because they have skin in the game.
There is a rather large difference between Google’s own OSes, software, and services; and the stuff Google uses. Google has the resources to mitigate problems with what they use from others much faster than most customers of the their competitors.
