Regarding operational flexibility, the DT-enabled system achieved a flexibility power of 20 MW per process, fully meeting the target value and remaining within the acceptable reference range (82.6–62.6 MW). The flexibility activation time was measured between 41 and 50 minutes, which is consistent with the target and reference interval of 45–60 minutes, indicating timely and reliable system responsiveness. Most notably, the Digital Twin accuracy, evaluated using the Mean Absolute Percentage Error (MAPE), reached 98.98%, significantly exceeding the target threshold of 80%. Overall, these results confirm that the Digital Twin provides accurate, reliable, and operationally effective support for flexibility management within the CELSA context.