They have officers in the army too :o

Again, speaking from my experience with modern day militaries as opposed to UC Century militaries, but the idea of someone making SGM before the age of 30 is completely unheard of (It typically takes a solid 20 years of experience to make Sergeant Major). But I think it would've been very possible for your character to have been an officer.

*shrug* Thats just my 2 cents though.

In regard to that rank listing, thats just how the cookie crumbles technically. A Sergeant Major with 20 years of experience is still expected to salute a 22 year old 2nd Lieutenant, simply because while he's at the top of [i]his[/i] chain of command (the enlisted branch), he's still beneath the officer branch, which is 2nd Lieutenant through General.