I think when the doctor shocked Harbaugh's heart to get it back in rhythm, that shock went to his brain. Harbaugh would be stupid to bench Alex Smith for an unproven QB. Alex Smith is completing 70% of his passes this season, averaging 8 yards per attempt with 13 td's and only 5 interceptions in 9 games. Before he left the St. Louis game with the concussion, he completed 7 out of 8 passes, 9 yards per attempt with 1 td and no interceptions. The game before that he completed 18 out of 19 passes, over 12 yards per attempt with 3 td's and no interceptions.
Maybe Harbaugh is just playing with the media and laughing about it behind their backs. You don't bench Alex Smith with the way he helped them to nearly get to the SB last season and the way he greatly elevated his game this season. In two playoff games last season, Smith threw 5 td's and no interceptions.
I've seen it happen many times before where a backup QB gets a start, plays well and as he has to learn more and more of the playbook and the coaches ask him to do more and more they melt down. Kaepernick hasn't proven anything yet except he played one good game.
Harbaugh is not that stupid to do it. Like I said, he's probably screwing with the media and laughing about it behind their backs. Or Smith's concussion is worse than they are letting on to and he may miss a couple more games anyway.