That's actually a very good point which never crossed my mind - no idea how 968s react to battery voltages which drop but on more " modern " cars there are numerous issues which cause havoc with all sorts of warning lights being triggered, or forcing the car into limp / safety driving mode, and other crazy stuff like that which seems to have no relationship to a battery , but it does !
Checked the battery voltages, charging was where it is supposed to be, and resting was 12.5vdc using a Fluke model 10 multimeter. For comparison, my wife's car was 12.7vdc at rest, so I think the 968 battery is still in good enough shape to allow the airbag module to reset, if it was so inclined.
I will probably pull the clockspring and check continuity this week. If that checks out I will try swapping one of the impact sensors with a known good one.
I suppose the good news is you can test the impact sensors without having to remove them. Those safety nuts will likely prove to be a challenge to remove should it come to that.