It's a completely new option that will eventually replace "Button Off Sets This To Default" (hopefully, but that functionality will have to be conserved).
This can work with momentary supercontrol buttons.
With Toggle Buttons
If the supercontrol is a toggle button:
the on value will set the subs to default. The off value will be respected.
If the toggle is "send on only" then it will take two presses to reset the sub to default. The second press has no effect.