If I'm not mistaken:
The command you're referencing (set band-steering wlan31 1)
is a command that is run on the AP itself and not on the controller.
Configurations/Commands of that type are lost after any AP reboot, which would include firmware updates.
If you can achieve your band-steering goal via controller based configs, that would be preferrable.
I don't know how it works if you attempt to configure band steering both from the controller and directly from the AP but:
I believe that "band balancing" is the same thing as "band steering", just that the feature was renamed going from one Ruckus firmware version to the next.
So, turning on "band balancing" should turn on "band steering".
This contradicts what Kristijan said.
If anyone has authoritative information, please let me know and/or correct me on this point.