IMO, Audit Note Stems (http://www.noteworthysoftware.com/nwc2/help/MNU_AUDITSTEMS.htm) would be improved if it ignored Grace Notes. The few grace notes that are set: Stem=Down, are set that way for reasons that have little to do with transposition and clef changing, which is what 'Audit Note Stems' is designed to assist.
If one really wants to remove stem directions from grace notes, repeatedly invoking Find: |Dur*Grace*Stem= and removing any stem direction, takes only a few seconds.