I don't disagree. My answer was based on a Watsonian perspective. Harry -- as the Operations Officer -- should have been promoted to at least JG by the end of the journey, which could easily be the case for Parry the Operations Officer/Pilot, but is less certain for Keskim the Yeoman or Harrix the Cook.
However, in your model there's no reason other than racism holding back Harry/Garrett (which AFAIK even he doesn't claim) there's no reason why Parry, Keskim or Harrix would be less vulnerable to "Someone needs to be the Ensign".
However, in your model there's no reason other than racism holding back Harry/Garrett (which AFAIK even he doesn't claim) there's no reason why Parry, Keskim or Harrix would be less vulnerable to "Someone needs to be the Ensign".