You got it, it's a smoke-and-mirrors screed to justify the lack of dependency management. 'One giant repo' might work ok in Perforce, but it's bad in git and SVN--forget about it.
Au Contraire. Google (and I'm assuming Facebook) have very detailed dependency rules that are explicitly described in files in nearly every directory throughout the codebase. There's no way you can do massive cloud compiles without this kind of information.