The WC game was a little different though, they only had certain pitchers available because they were trying to save some for the ALDS. I could see them throwing SJ for a couple innings at less than 100%, but then deciding they don't need him in the ALDS less than 100%. Not sure really, just trying to make sense out of it.
It's more likely that Buck trusts the veterans more than the rookies (he's got a reputation for that) and when he had to choose went with the veterans.
I don't think the first paragraph makes sense. If Johnson wasn't 100%, then why would they trust him in a key situation during a winner take all game but not to be one of 8 relievers for the ALDS? Plus, he should be more healthy now compared to then.