Rich... you are making an assumption though... that's the whole point. There are rule sets that the person is a re-entering starter. Heck, we use that the term in the tournament rules for LL and it is used in the Big League rules, as well.
YES, the principles in the sub rules are entirely different. But if you are spelling it out from LINE 100, it starts with "any player entering the game after the first pitch is classified as a substitute, regardless of whether they are entering the game for the first time or they are a re-entering player."
And in THAT is where the RIM (and the new A.R. notes) are VITAL to teaching people rules and regulations.