Hi,
As of my knowledge, OMBZ configuration will check the IR for goods/service items only. It wont check the IR posted for planned delivery cost, parked invoices etc. In case of intra company STO, there is no invoice for goods/service items and system will allow to cancel the GR even though the IR for planned delivery cost is posted.
You may test the same scenario with a normal PO and check the system behavior.
Regards,
AKPT