There is an MRP reschedule field for Purchase Order lines. There should also be a reschedule field for work order material lines.

Reschedule (for PO lines)

Select this check box to restrict the MRP (Material Requirements Planning) report generation process to recommend that this purchase order be rescheduled with a Push Out action. Clear this check box to allow the MRP report generation process from recommending that this purchase order be rescheduled with a Push Out action.

Companies need to lock down the schedule for certain firm planned work orders. There is no way to do this without a reschedule field similar to what you have for PO lines

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