Why does the function checkConsentersMatchPolicy in fabric-3.0.0/orderer/consensus/smartbft/configverifier.go include these three lines of code, which prevents leader rotation?

if configOptions.LeaderRotation == smartbft.Options_ROTATION_ON { return fmt.Errorf("leader rotation must be turned off for this version or be unspecified") }

Are there any functions that are not yet fully implemented?