Jeez, I hate the printed word sometimes. I'll have to write a book to explain what I meant. In short, in this situation, we're agreeing that there will be two outs after the ball is hit to the SS. So, no matter what, there are two outs. If the runner wasn't sure, for whatever reason, that he could score, he should have held because the number of ways he could score with two outs, runner on third didn't change. Had he been on 2nd, taking 3rd would have been a bigger deal because he can't score on a balk/wild pitch/passed ball from 2nd. That's still a horrible explanation of what I meant but maybe it's more clear.