Can we lock a period and still match unmatched transactions originated in the locked period later?

Summary:

Can we lock a period with unmatched transactions and once those transaction finally appear in the "other" system, have them match with those previously unmatched transactions without opening that locked period to perform the matching?

Content (please ensure you mask any confidential information):

We commonly have transactions that don't get matched for many months after a period is completed. We want to be able to lock periods as we are told that is a best practice, but are being told that we have to unlock an old period when we are ready to finally match. This seems inappropriate as during the original period, those transactions were truly outstanding and unmatched and only during the later period did the resolution/matching occur.