The latest documentation here includes the following text:

Dynamic controller quorums

This mode enables dynamic scaling of controllers without downtime. New controllers join as observers, replicate the metadata log, and eventually become eligible to join the quorum. If a controller being removed is the active controller, it will step down from the quorum only after the new quorum is confirmed. 

The text is confusing because for new installations a reader can think the dynamic configuration can be enabled, because nothing has to be migrated.

Documentation should explain explicitly that even for new installations on OpenShift, the dynamic configuration is not available yet when deploying Kafka on OpenShift with KRAFT mode, and the static controller quorums will continue the active and applied configuration in 2.9.0.