When do you go top-down vs. bottoms-up? It hinges on three variables: ambiguity, urgency, and the team's experience in this problem space. It's not a binary choice, but a sliding scale to move along as conditions change.
Directive: When the problem is hairy, poorly defined and time-sensitive. In these moments, convergence matters more than exploration. The job is to reduce ambiguity, set constraints, and create a tractable problem the team can execute against.
Bottoms-Up: When the problem is well-scoped and the team has demonstrated competence in this terrain. Here, over-directing slows things down. The work benefits from trusting the experts, local judgment, iteration and letting the shape emerge from doing.