Utterances vs. Sentences

I don't know whether to be skeptical of the Bedford Glossary, or the idea of Bahktin being considered a Russian formalist. The Bedford Glossary tells us that Russian formalists are "focused on form (rather than content) of literary works." From my reading of Bahktin, it seems as though he is more concerned with the idea of analyzing how text  is used to communicates. This communication seems to be done through a sentence/utterance's thematic content, rather than form.
 Bahktin puts a heavy emphasis on making sure his reader's understand the relationship between an utterance and a sentence. I quote, "The sentence as a language unit is grammatical in nature. It has grammatical boundaries and grammatical completeness and unity. (Regarded in the whole of the utterance and from the standpoint of this whole, it acquires stylistic properties.) When the sentence figures as a whole utterance, it is as though it has been placed in a frame made of quite different material. When one forgets this in analyzing a sentence, one distorts the nature of the sentence (and simultaneously the nature of the utterance as well, by treating it grammatically. A great many linguists and linguists schools are held captive by this confusion, and what they study as a sentence is in essence a kind of hybrid of the sentence (unit of language) and the utterance (unit of speech communication.) One does not exchange sentences any more than one exchanges words"(Bahktin 74)
What I believe Bahktin is saying is this: A sentence viewed grammatically has no content because the viewer is limiting him/herself to the stylistics, syntax, diction...etc of the sentence. Bakhtin is suggesting that in order to better understand a sentence, one must not only view it grammatically, but as a hybrid of a grammatical sentence and a verbal utterance. If you do not consider the hybrid nature of the sentence, then you cannot truly understand its thematic content. Thematic content arises not from the grammatical sentence alone, but from the corresponding utterance that is part of a larger dialogue, a dialogue that gives it content by providing the vuewer or listener with a context that shows the intent of the speaker/writer. This concept is what Bahktin refers to as "a chain of speech communication of which the utterance is an inseparable link."