Although this is in the 'Adjust outputs' menu, it is really part of the 'Adjust resolutions' data, and thus the unit first needs to be told the resolution number to adjust.
First send the 'Image to adjust' command, so set the resolution number that needs the output type changing:
e.g. For NTSC:
Then send the 'Output type' value required:
e.g. for RGBHV: