What makes more logical sense: that your Punter handle placekicking duties because they would have practiced for it all year at least once per week with a normal coaching staff just in case, OR - "oh shit, the kicker got hurt, can anybody placekick at all? really, just Heath? anyone else?"
The punting skill set is at least related to the placekicking skill set. Safety is in another galaxy.
And let's be real here. Garrett had no plans for an emergency, and hasn't had his punter practicing emergency kicking. He had to put the call out, and Heath was the only one who could do it. Shit, Garrett probably found out at the time of the injury that Heath had some competency. He got caught with his coaching 101 pants around his ankles again. He only got away with it because SF was horrible today. If this had been a game that came down to last second FGs we likely lose.