It depends a bit on the context. Generally, I very much like your approach!
Let's provide some context:
For a structure question
Top-down means that you go from the more general and abstract ideas to the more concrete and tailored ideas that are relevant to answer the initial question. By using numbers and signposting the way you do, you make it easy for the interviewer to follow, intervene or ask follow-up questions.
For a recommendation, implication, hypothesis, etc
Top-down means that you would start with your key point first, then provide supporting arguments.
Generally, consulting communication is mostly top-down, especially on the level with senior executives. When collaborating with clients on less executive levels, consultants sometimes switch to a bottom-up approach, first explaining their logic and rationale, then providing their insights, request, etc. The latter, however, is not relevant for case interviews.