Hi,
You have configured release strategy for PO. The release order is nothing but a PO created based on contract. PO will go for release, based on the release characteristics, even though it was created based on contract / PR / other PO's or without reference. Its standard system behavior.
The contract is a type of outline agreement created based on the agreed terms and conditions for a long period of time. Based on this agreement, you are creating PO (release order). I think the release of this PO is to be done logically.
Refer the similar thread: MM:Release Strategy for Release Order again Approved Contract
Regards,
AKPT