Not sure this will help with your question, but, here goes anyway:
In the All Metal Motion mode, you have no control over the # of Tones, Disc or Notch, however, I do believe you can still do the Fast Grab (auto Ground Balance), but, why? In the Disc mode, I think the Audio Pitch, manual GB and Threshold carry over from All Metal, but, the Sens. is set seperately for Disc. or All Metal. The reasoning (just my thoughts) is for people like me that like to question a target with a Disc. and All Metal comparison.....especially, if I am running in the Disc. mode. With a quick push of the Menu button and turn of the Settings knob, I can check the target in Disc, then, All Metal, or, back and forth, to help me decide whether I want to dig it. I run in All Metal mode a vast majority of time, even in moderately trashy areas. In the really trashy areas I will Disc. and use the All Metal motion mode to help me ID the target.
Does that make sense?