Isn’t that different than tacet? It’s been a good number of years since I was reading charts, but I understood it to mean, don’t play chords, and additionally, if there is a single line of music, play that.
The chords appear on top of a top line vocal part, which both vocalists and instrumentalists use. Sometimes the vocals are present but chords are not required.
N.C might well be an option - I was not aware that could be entered in the popover…