Explanation/Reference:
If revenue on this invoice was deferred due to unmet payment-based contingencies, then Receivables always debits the unearned revenue account for the full amount of the credit memo, according to the initially assigned revenue scheduling rules.
Note: If you issue a credit memo against an invoice that had revenue automatically deferred upon import, then the impact of the credit memo differs depending on the original reason for the revenue deferral. This applies only if you set the Invoice Accounting Used for Credit Memos profile option to Yes.
References: https://docs.oracle.com/cloud/farel8/financialscs_gs/FAOFC/F1113011AN1CFB0.htm