^ A bunt is far more of a concession than a sac fly is.
Colabello's sac fly yesterday, for instance, was 10 feet from being a home run. A sac fly is a legit attempt at driving a runner in. A sac bunt is conceding a whole third of your inning to move a runner to another base. Huge difference in intent, execution, and result. A sac fly and a searing line drive are inches/milliseconds of timing apart, and something a batter can't really control. A bunt requires a deliberate stance, which the defense is probably already prepared for, and, at most, earns you a single base.