Note that the FRA flight (454) due in at 12:55 is very often significantly delayed.
A friend was taking it to meet me in SFO, by the time he got through and to the car rental place it was 3pm; this is common according to the flight stats website. It then took me 5 hours to drive to our destination due to hitting rush hour traffic on the way out.
Fair to say he was pretty tired by the time we arrived - but this is the earliest flight we could find getting into SFO; without leaving a day earlier of course.
Also, I've never had a smooth connection through FRA. The security section there is extremely obnoxious and the boards never seem to show all the connections. MUC or direct (on the BA flight for example) is a much better choice imho.