For instance for a Burton Custom board, you can ride it with Cobra Sharks, Customs, Missions, Cartels, Malavitas, etc. I think most of us could agree that any of those bindings would for the most part pair with the Custom. It's up to the user to decide the best binding with the features, stiffness, and price point.
Yeah but a Burton Custom is a 5, right in the very middle, so obviously anything that isn't at either extreme end of the spectrum will work fine with it.
The OP was pairing a soft board with two options in bindings. One of them stiffer than the other. Sure it will work to have a stiff binding on a soft board, but in general you'd want to have a more closely matched setup.
If anything it's just a waste paying more to get stiff bindings for a soft board or vise versa.