Scope fidelity
A prototype becomes valuable when its evidence outlives its code.
RDD is not excited by demos because they look real. It cares when a working model exposes enough behavior for people to reason about what they are commissioning.
Three fidelities
It looks like the intended product.
It behaves enough to expose rules, states, permissions, consequences, exceptions, and workflow semantics.
It covers enough consequential product surface for stakeholders to reason about delivery boundaries and obligations.
Why this matters
A visual prototype can help people react to layout, information hierarchy, and experience tone. It often cannot reveal whether an approval belongs before or after assignment, whether a supervisor can see regional data, or whether a "closed" case can reopen after appeal.
A Build to Learn artifact can expose these issues because it contains working roles, states, dashboards, forms, representative data, and enough business logic to provoke operational disagreement.
Still not production
A broad working model is not production reality. It is a model of intended reality. Its job is to make mismatch observable while the model is still cheap to change.
That is why RDD pairs early learning with Reality Checks and production-grade Build to Deliver. Looking right is never the same as being secure, scalable, resilient, integrated, or maintainable.