Group on Fader

Can someone explain to me the ability to Put a group on a fader?
Like on the grandMA, you can move a Group of fixtures to a fader and it automatically becomes an intensity controller for that group.

I see that you can do similar on a Road Boar. Group 1 Move To Fader 1. Will put the group on the fader. But It doesn't do anything when I use the fader. In the Faders option it is set to I Fader.

Am I missing something?
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