Digital Light & Color

I have difficulty in understanding the advanced brighness curve sharpening

In the brightness curve transformation (advanced mode) there are sharpening controls (Radius, Threshold and Detail).
According to documention on the Threshold slider :

If the difference between the input and sharpened image is less than the threshold, no sharpening is performed. When set correctly, this reduces the amplification of noise in relatively smooth areas of the input image while still sharpening areas with distinct edges or texture.

and

Sharpening threshold sliders have an additional feature which lets you feather the boundary between the affected and unaffected areas of the image, in order to make the effect look more natural. While you can create a sharp cutoff if you want one, you can also specify a transition region where the effects of the transformation are blended with the input image.

If the Threshold is set to 100%, there is full sharpening - how to reconcile this with the threshold slider help quoted above " ... no sharpening in performed"?

Why isn't there a gray zone (black and white sliders) ?

Thanks

The help file could be more specific about this and I will add some additional description.

In Multipass Sharpen, there are two Threshold sliders -- a Blur Threshold and a Sharpen Threshold.

The Blur Threshold corresponds to the one in Brightness Curve Advanced Mode and it does not have a gray zone.

The Sharpen Threshold is the one that has the gray zone -- there is nothing in Brightness Curve Advanced Mode corresponding to the Sharpen Threshold.