I'm pretty sure you know that isn't really true. No matter how much power assistance there is, if your steering suddenly had no centering force at all it would feel a lot different.
That said I don't think the ffb is exceptional in AC, judging purely from the tech preview.
Sure there is resistance, but mostly, when my friends or 'hardcore'-simmers say : Dennis try this out, this is the most amazing feel I've ever felt'' It's usually over exaggerated, I'm sure Kunos has made something fantastic here and I'm probably just blowing the bubbles, but there is NOTHING that can feel 'real' compared to a racing car, there is just too many elements you can't simulate, sadly.
Well I agree to an extent, but ultimately what happens to the steering via FFB should be dictated by what happens to the front wheels. I'm perhaps like you in that "effects" add nothing. Vibration should only be felt if it exerts a torque on the steering column. What matters, and what makes the difference, is the response and reaction to those forces, but ultimately it should be the tyre model which dictates what the FFB is like.
A good FFB system should simply relay those forces to your wheel with as little latency as possible. For me LFS is far better in this way than AC. A sim should prioritise the FFB, not just say "only 50fps? Guess you don't want steering response or feel anymore then".
I also think that with the right hardware and software there is no reason why an FFB system cannot accurately simulate every ounce of "feel" and force you experience in a real car.