I'd like to take another look at what fluency is and is not. Fluency is easy to define, easy to confuse, but difficult to achieve.
Fluency is, essentially, the ability to speak like a native speaker. But that does not mean exactly the same as a native speaker. Speaking exactly the same as a native speaker is language mastery. So, a fluent speaker need not be perfect, nor have as large of a vocabulary as a native speaker.