Answer
It should prove the vendor understands a real workflow, not just a clean schedule. Buyers should ask to see a dependency, an exception, an alert, a recovery path, and an audit trail so the demo shows what happens when the process is imperfect, because that is where operational fit becomes obvious.
A credible demo should also connect the workflow to business consequence. If the presentation never moves beyond a happy-path job chain, it has not proven that the software can handle the pressure points buyers actually care about.