That part is confusing, though. Right above the checkbox it seems to state, unequivocally, that a forum thread will be created whether you like it or not. It looks like a statement of fact. And then the checkbox is simply giving you the choice to allow ‘discussion’ or not on that newly created thread; as in the thread will be locked upon creation if the checkbox is disabled. (We seem to have no choice in the thread getting created or not. The way things are worded and presented, it will get created.)
So, two different things.
You’re positive/sure that disabling “allow discussion” will result in the mod ‘not’ getting posted in the forum as a new thread?