This is the key comment in this thread. The article simply does not tell the full story In fact, Google even released a nasty little tool called "git repo" that coordinates simultaneous accesses to multiple git repos.
Sure, but even "only 80% of Google" in a monorepo is still bigger than the combined size of most everyone else's constellation of small repos. And the the separation of repos is based on deployment environment: Server, desktop, and smartphone, where code has almost no cross dependencies because the environments of software never communicate via internal channels.
The article is a fair assessment for "traditional" projects at Google (server-side? hosted? native? not sure the best term. Think "gmail" or "search" or "brain").
As mentioned elsewhere, Android and Chrome are huge exceptions in that they're a) open source and b) pretty much standalone products not closely tied to the rest of the Google ecosystem.