How would they not be able to use Linux anymore? With it being GPL and everything?
I'm hopeful EEE[1] is a thing of the past, but I can see why Google would hedge for the possibility of Linux and open source in general being pod peopled into an ecosystem it can't keep using. They're worried Microsoft will do to Linux what Google did to AOSP. Golang's dependence on importing stuff from GitHub is already a threat.
[1] https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguis...
Then Google just doesn't take that patch and forks the kernel. Google already has its gLinux team with their own Debian-based Linux distro, and Google has a successful history of leading OSS projects.
With Q, the Linux kernel is the only GPL thing still standing.
No need to worry about Microsoft.