A Gantt chart excludes most of the room
Programme reviews tend to involve a planner defending a bar chart to people who cannot verify it. Site staff who know the sequence is unbuildable often cannot articulate the objection in the chart's language, so the objection does not get made.
Geometry makes the sequence falsifiable
When activities are linked to model objects, the sequence plays back as a build. At that point a foreman can point at the screen and say the crane cannot reach that corner in week nine. That is a specific, checkable claim — which is exactly what a programme review should produce.
The cheap wins are in temporary works
Most 4D value in our experience comes from scaffold, crane position, site access and laydown — the things that are not in the design model and therefore never get coordinated. Modelling them roughly is enough to find the conflicts.