No, you can build either top down or bottom up; but tell from the top down
Stories can be created from the bottom up or from the top down. Stories are, however, told from the top down, usually beginning with the context, the trigger, the question and the answer before moving step by step into the details.
Very often you will begin forming a storyline at the bottom by sorting ideas into groups to help identify the themes and messages within the idea set. This process enables you to work toward identifying the overarching answer, or governing idea, at the top of the storyline.
Once this bottom-up clarification (or problem-solving) process is complete, you are ready to tell the story from the top down.