I don't think that comment was expressing a clear opinion either way, just stating that as long as Google is basing their software on Linux they are definitely legally obligated to follow certain rules (e.g., no direct linking of proprietary drivers provided by a vendor) and vaguely politically obligated to follow others (e.g., there's a fair bit of C++ in Magenta; adding C++ to a fork of Linux is technically straightforward but would upset people and also make it hard for patches to your fork to go upstream).