a better point is the preface to the guava project docs:
"The Guava project contains several of Google's core libraries that we rely on in our Java-based projects"
given that, it is fair to say "this is essentially an internal codebase, and we would prefer to develop it ourselves so that it fits our internal practices and standards; however, it is an extremely useful set of libraries, and we are happy to share it with the open source community so that you can use it too, if you like"
"The Guava project contains several of Google's core libraries that we rely on in our Java-based projects"
given that, it is fair to say "this is essentially an internal codebase, and we would prefer to develop it ourselves so that it fits our internal practices and standards; however, it is an extremely useful set of libraries, and we are happy to share it with the open source community so that you can use it too, if you like"