I disassembled a 67 switch it may or may not be the same.
IIRC the extra ground is needed for situations where the switch is mounted to plastic. It provides the ground for the dome light switch cir to work ( but don't quote me on it)
Also at some point there was an internal change that caused the front parking lights to be on with the headlights, 67 they are off when headlights are on.
The thread I read on park lights with headlights on said there is a jumper not shown on most schematics from P to R to connect them with tail light circuit and not actually with headlights as it would draw To much for that circuit. Sounds right?