What dMax are you getting with ABW and on what paper?
dMax is paper dependent.
ABW will make dMax quite lighter than RGB value 0 pixels. It can not differentiate between the lowest shadow detail values and produces dMax easily.
Piezography only prints dMax at RGB value 0 so that it can print the tonal separation between all 256 values. RGB value 1 is actually lighter than 0 with K7.
You can not easily find your dMax in LR because it is a proxie you are looking at and the actual processing often differs from the histogram - so move the image out of proxie state in LR to Photoshop and then find out if you really have dMax pixels or not.
Complex answer to easy question...