Customer facing docs should indicate that customers need to upgrade to the latest z-stream before migration in order to get the most recent bug fixes.  This belongs as one of the bullet points under "Prerequisites" in section "28.6.2. Migrating to the OVN-Kubernetes network plugin" in the networking guide:

https://access.redhat.com/documentation/en-us/openshift_container_platform/4.15/html/networking/ovn-kubernetes-network-plugin#migrate-from-openshift-sdn

This new bullet could be linked to the upgrade guide at:

https://access.redhat.com/documentation/en-us/openshift_container_platform/4.15/html-single/updating_clusters/index.  

    All releases 4.14 and later should get this update