We are building the openldap-servers package and keeping it in plus as we wanted to ensure users will always have it available (same as what we did in 8 before it moved back to powertools). We provide it as an option as it wasn’t a guarantee from our point of view (at the time we were building Rocky 9) it’d be packaged in EPEL.
If a user wants to use the EPEL package, they can. If a user wants to use the plus package, they can. Each time the openldap packages are updated, our openldap-servers package is simultaneously updated.
I did face similar situation in Summer 2020, with CentOS Linux 8, and chose to try migration to the “389ds” (as back then nobody had openldap-server for el8). That was relatively easy.