NCF material doesn't have any sort of contact with the wires, and it's not a damping material either. All it does is remove noise, and this is easily measurable on an AC power quality meter.
I'd suggest it may be the damping properties of the stand and cover you don't like, maybe not the NCF material... Damping is indeed difficult to predict and requires some experimentation.
I have also read reviews that have mentioned the homogenous sound of the brace.
I also noticed that with the NCF outlet cover, although to a lesser degree.
It is a delicate line when a product removes noise, that I have experienced with other products also.
I have been using the Furutech carbon fiber cover for years and couldn’t live without it.