We just setup auto RF on all of our 12 controllers. My question is, is the controller group leader the only controller
that will display the "Last Group Updates" times? or should I see it on all the controllers?
You should see it on all controllers. Each controller has its own timer for running the Auto RF checks.
As an aside, I highly recommend that you disable the automatic updates. Running them manually once a week or so is usually best, unless you have a constantly changing or challenging environment. Client can occasionally be disconnected by the automatic updates, which occur every 10 minutes by default.