Fluency vs. Proficiency
What does it mean to be fluent in a language? Most people equate fluency with proficiency, but as an ESL teacher and a psycholinguistic researcher, I can assure you that there is a distinction. It is possible to be fluent without being highly proficient, as it is also possible to be highly proficient without being fluent.
Fluency, whether it be in reading or in language, refers to the ability to convey the message unhaltingly. When it comes to second language learning, a few major aspects of fluency lay in the prosody of the language, pronunciation, and the timing of dialogue. Indeed, it is even possible to be fluent in your native language in your home region, but not have fluency in a different region of the same country. I have fluency in a Midwestern dialect of English. If I were to travel to the deep south, I could easily hold a conversation, but I would not be considered fluent in that region. Fluency is impossible to attain without engaging in dialogue with a fluent speaker of the language.
Proficiency, on the other hand, is the primary focus of Duolingo. This is your ability to understand and communicate in the language. While I would not be fluent in the dialect of the Deep South, I am still a highly proficient English speaker. Proficiency is best practiced through reading and writing. Children may be fluent in a language but not highly proficient, as they lack a certain level of vocabulary that comes with understanding the depth of the language. Of course, the vocabulary covered in the language tree will not provide complete proficiency in the language either, but it will provide the foundations that, along with the reading and writing practice in the Immersion section of the website, can expand your proficiency.
Is your goal learning goal one of fluency or one of proficiency? Do you want to hold a conversation with the ease of a native speaker, or do you want to understand the depths of what the language has to offer? Both are excellent language goals, and it is important for you to recognize your own purpose in order to set a language routine that will allow you to achieve those goals.
Totally agree with you in every way. I consider myself fluent in Spanish only because I'm a bilingual native speaker and can hold conversations easily. Even still, I'm not the most proficient (which is why I'm here in the first place!) and I'm definitely not fluent in most dialects of Spanish, especially because Argentina is totally different from most. I think that to be "fluent" you should have a certain level of proficiency, of course. But if you have no grasp on colloquialisms/expressions/anything that isn't literal, the conversations you'll have with native speakers won't have much depth. These things have to be learned through immersion. No amount of studying (or TV show watching) will give you that experience. Even if you observe peoples' interactions and memorize slang words or whatever, it'll still probably come across as artificial.
Personally I wouldn't consider someone fluent in a language if the extent of their knowledge of a language is limited to what they've learned in a course or two. I agree that language courses emphasize proficiency over fluency, however you define the latter. Feel free to prove me wrong, this is just in my experience of interacting with Spanish-speakers vs. students taking Spanish classes.
I think my own goal is mostly just to improve my general Spanish proficiency in terms of grammar, writing and reading. I don't think fluency is an issue for me at this point. I'm also really interested in learning Portuguese! I haven't decided what my Portuguese goals are, though.
I think this is a bit to "matter of fact", as there is no official, specific, definitive, agreed upon, definition of fluency,
But, other than that, I agree that fluency and proficiency can be thought of as being separate things to some extent (obviously there is some overlap in many situations). I also think that one aspect of fluency is being able to get your point across, not worrying about how graceful you are. By this I mean that, if you lack the vocabulary or knowledge to express something, you can improvise fairly smoothly and find another way of expressing it, whereas someone with proficiency whom also lacks the vocabulary may be at a loss for words.
Nice mentioning dialects of English by the way, as that is something that is too often overlooked. Of course, some dialects and accents of English are fairly similar, but others, like some found in the deep south that you mention or in parts of Australia, are quite distinct.
I agree entirely, personally I dislike the word fluency, since it is such an ambiguous term. I think it derived from the word "flow", as in flow through the stream (or language) easily, rather than fight the current.
Anyway, I prefer to use the term proficiency, if I had to define my average proficiency in all aspects of the languages I know (Portuguese, and English), I would say I'm an intermediary in both. However, as odd as it may sound, my ability to write is higher (between intermediary and High proficiency) in English than it is in my native language, my ability to read is about the same in both (intermediary), and my ability to speak too.
In my opinion, it seems as if the term "expert" cannot really apply to languages, a linguist (highly proficient) would be the closest to the term, and yet even that individual will struggle to understand a teenager's lingo (with all the new terms that arise everyday), and domain specific (technical) terms.
Just to clear up a common misconception, being a linguist has almost nothing to do with 'knowing' languages. Linguists study languages, in the sense of studying them to find out things about them, not in the sense of studying them to learn them. A linguist may have proficiency in languages other than their native tongue and sometimes it may be necessary for the work that they are doing, but not always.
The most common response that linguists get when they say that they are a linguist is 'How many languages do you speak?'. They hate it because it is a question mostly irrelevant to their work and continually demonstrates to them that people don't understand what they do.