ATM, when you reset a reconciliation, the record in Fact_Reconciliation is only updated (MatchCode is set to null).
So the Fact_Acct_ID is still present in the table.
Means that you are not able to delete an allocation ; eg :
Trx.saveError: DeleteErrorDependent - ERROR: update or delete on table "fact_acct" violates foreign key constraint "factacct_factreconciliation" on table "fact_reconciliation"
Détail : Key (fact_acct_id)=(1138014) is still referenced from table "fact_reconciliation". 
With attached patch the record is deleted in Fact_Reconciliation (as discussed with .