To have the ignition on the left is a kind of status-symbol based on the race car history of Porsche.
In the 20s the drivers had to run to their cars and to start them. To speed it up Porsche but the ignition button on the left side.
As racing was/is expensive, the left side button became a kind of exclusive symbol.
And C-bodies where big and maybe they thought "we need to make them appear more exclusive".