No. The number of buckets is not a scoring criterion. Two strong branches can be better than four weak ones if they cover the problem and lead to useful analysis.

The structure should be as simple as possible while still being complete enough for the objective. If two branches leave a material driver uncovered, add another one. If they do not, do not invent a third bucket for appearance.

Explain the logic behind the structure and show how each branch connects to the decision. That matters more than the count. If useful, this guide on case structure vs. case framework gives more detail.

Two buckets is fine if it's actually complete. forcing 3 looks more fake imo.