Your shadows called. They want their detail back.
This is just a short post about why I ditched Espon's ABW mode when I got serious about making digital black and white inkjet prints. I have been making custom QuadToneRip profiles since 2007, and have been asked more than once if they were silver prints (the first time was back in 2009 from a museum curator, who at one time was an assistant curator at MOMA—not bragging, just putting things in perspective).
Aside from QuadToneRip's ability to finely control print color when using Epson Ultrachrome K3 inks, its ability to create custom media settings for different papers and fine tune the final linearization simply allows you to make better prints.
The following jpegs are scans of actual prints made with a calibrated scanner with no additional levels adjustments, either in scanning or post processing (aside from downsampling and converting from the scanner profile to sRGB for web display). These scans compare prints made with Epson's ABW mode and a blend of three custom QTR profiles. Both prints are on Canson Photorag Platine‚ my favorite paper for making glossy black and white inkjet prints. Then take a look at the density/luminosity graphs of 2% 51-step targets, and see how the shadow detail is blocking up in the ABW print while the QTR print is smooth to the very end (without additional ICC profiling, correction curves, or other "transfer functions"). Printing with QTR allows you to carefully control how detail smoothly transitions into the darkest shadows of your prints.
I hear people all the time say that ABW is fine for them and they don't see a need to bother with QuadToneRip or making custom profiles. I say that the mediocre always looks fine until you compare it to something better. Why lower the bar?