The source clarifies that literalness and figurativeness are fundamentally classifications of the ascription. Speech is described that way because it contains such an ascription.
All the words of a sentence may retain their established lexical meanings even while an action is attributed to something not regarded by the speaker as the true bearer of that action. Calling “spring” or “rain” a lexical metaphor by itself does not address the predicate–subject relation.
Keep two distinct questions in view: how a word is used, and how an action is attributed.