No. As mentioned in the documentation, optional sections that aren't spoken return a blank segment.
E.G. speaking "navigation screen" would have "{CMDSEGMENT:0}" return "" (blank), "{CMDSEGMENT:1}" return "navigation", "{CMDSEGMENT:2}" return "screen", and "{CMDSEGMENT:3}" (as well as all subsequent segments) return the literal text "Not set".
If you're unsure as to the output of a given token, you can use the "Write a Value to the Event Log" action to show its value in the log on VoiceAttack's main window.