Bug tracker
config_dbms_version doesn't get updated automatically (fix completed in vcs)
I assume that value should update automatically with each database upgrade.
Comments / History
Within the updater phpBB checks this value to make sure the schema is valid and in case of incompatibilities notifies the admin of required actions.
If we would update it constantly an admin (and phpBB) would never know if the schema is correct, then this variable could be removed.
Thank you for the explanation!