Interesting because even in the early game, new commanders do not always appear at the end of the list.
Obvious example: in the game I was testing this in, my awake pretender appeared down in the lower half of the list.
I'm not sure what order I recruited the others, but the researchers with a star of experience are not all at the top.
Hmm, so that's the second time I'm wrong then. Apparently unit IDs are freed for reuse immediately upon the death of the previous owner, which, now that I think of it, is what happens since I've seen the same behavior myself.