A sentence may be grammatically declarative yet not be uttered merely to give neutral information. Its form may be used to express regret, longing, grief, complaint, or some other communicative purpose.
A poet who says that his longing traveled with a departing caravan is not necessarily concerned with reporting a literal journey of a measurable object. The utterance conveys attachment and the pain of separation.
This observation underlies an objection to narrow definitions of compound figurative language. Not every departure from ordinary reporting must consist of resemblance between two scenes; sometimes the rhetorical shift concerns what the whole speech act is meant to do.