Re: Commodores in command of Starships?
According to Wikipedia
Field officers, also called "field-grade officers" or "senior officers", are officers who typically command units that can be expected to operate independently for short periods of time
Naval and coast guard senior officer ranks include captain and commander. In some countries, the more senior rank of commodore is also included.
Perhaps another possibility besides the aforementioned ones is that they intended "senior officer" there to be synonymous with "flag officer"?