3573151 - Plan cost rate is used for order confirmation

When doing order confirmation, system use plan cost rate maintained in APP 'Manage Cost Rates - Plan'.

SAP S/4HANA Cloud Public Edition 

This is a standard behavior that system use plan cost rate for activity confirmation and shown as actual cost in APP 'Cost Centers - Plan/Actual'.

Before period end closing, the activity confirmation uses the plan cost rate for postings and user can execute actual cost rate calculation based on planned costs and activities. The resulting cost rates are used to value actual activities.

Actual cost rate calculation calculates iterative cost rates for activity types based on the actual costs incurred and the actual activities performed.
All activity exchanges between cost centers are taken into account.

After actual cost calculation and actual costing run, the activity can be  revalued with the difference between plan and actual cost rates.
By revaluing the actual activity with actual rates, sender cost centers will be fully balanced.

See more information in 

Actual Costing: FAQ

Actual Cost Rate Calculation - Cost Centers

Order confirmation, activity type, cost rate, manage cost rates. , KBA , CO-PC-ACT-2CL , Actual Costing (Public Cloud) , Problem