S-Curve Accuracy: High Level vs. Detail

The figure illustrates two S-curves for a project:

The red curve and blue bars are derived from the distribution of the Engineering, Procurement, and Construction (EPC) budget.
The black curve and orange bars are generated from the detailed project schedule.

Red Curve/Blue Bars: Budget Distribution (E, P, C) | Black Curve/Orange Bars: Detailed Resource-Loaded Schedule

Which one represents the project plan progress more accurately? Obviously the second one.

Decision Risk Can a PM make accurate decisions based on high-level S-Curves? Most likely not.

Success Rate The chance of delivering a project successfully using high-level curves is dangerously low.

Cost Engineers who cannot obtain a correct S-Curve from the planning team.

Planning teams unfamiliar with the mechanics of Resource Loading.

Consultants who fabricate curves to avoid embarrassment, only to blame the project later.