RE: OS != Filesystem

An OS is software that manages all your computer's resources. In the context of modern consumer PCs, that includes things like scheduling, multithreading, virtual memory, interrupt handling, and providing abstraction layers for all the various hardware systems in a PC.

Regardless of the fact that Unix systems view all device I/O as "files", having an online file system has pretty much nothing to do with being an actual Operating System. While Google could conceivably have some form of online OS (I can't really imagine how that could possibly work, but it is Google, so who knows...), this article doesn't actually say anything in support of this.