I've heard cheng and chi translated in other ways, like "ordinary" vs. "extraordinary", "direct" vs. "indirect," so maybe "unpredictable" doesn't really apply here. I read it as being more about conflict within an ever-changing environment. If the world is constantly falling out of order, the advantage doesn't go to the one with the most consistently rational strategy, but the one who responds to change the fastest. So instead of making your opponent confused about your strategy, the goal is to degrade his perception to make him unable to keep up with reality itself. This is all very theoretical and abstract though.
Your opponent becoming so paralyzed by the fear of not knowing what you will do next and thus doing nothing also fits the OODA loop in a completely different way, but isn't really cheng/chi. This is also touched on in Art of War, so it's not like they are conflicting ideas.
I disagree that this is a good idea. I think acting unpredictably gives your opponent a reason to look deeper into your strategy which ultimately might end up sinking it. If you perform an unpredictable move it should be for a hard and fast strategic gain.
Ideally you should move in a fashion that is entirely predictable by your opponent without incurring significant loss to yourself. This will caused them to be surprised when you eventually break from your predictable normal activities and perform an unexpected maneuver.