This is exactly it for me as well. I also communicate with LLMs in full sentences because I often find it more difficult to condense my thoughts into grammatically incorrect conglomerations of words than to just write my thoughts out in full, because it's closer to how I think them — usually in something like the mental form of full sentences. Moreover, the slight extra occasional effort needed to structure what I'm trying to express into relatively good grammar — especially proper sentences, clauses and subclauses, using correct conjunctions, etc — often helps me subconsciously clarify and organize my thinking just by the mechanism of generating that grammar at all with barely any added effort on my part. I think also, if you're expressing more complex, specific, and detailed ideas to an LLM, random assortments of keywords often get unwieldy, confusing, and unclear, whereas properly grammatical sentences can hold more "weight," so to speak.