I know little about the grounds on steering columns but I've never heard of using a bearing as part of an electrical circuit..

The 76 wiring diagram shows the ground through the combination switch.  

73 shows similar but they actually show a connection between the ground circuits.  Seems like there would be a sliding contact like for the turn signals, to ensure a ground circuit.  Just offering another possibility.  There might something buried under the mechanism.  I had mine apart long ago but can't remember what was underneath.

Whatever it is would not pass much current.  Just enough to trip the relay.