Point is Andy, if the car thinks the belt is plugged in it WILL fire the airbags etc.
Unplugged and it won't/shouldn't ergo no airbag decapitation.
What Dave is saying is that he uses a dummy buckle to silence the warning; it serves no other function; as far as the car is concerned, the driver is wearing a seat belt and will fire the airbags etc as designed.
this is dangleberries and DANGEROUS advice
the airbags will deploy even if you have no seatbelt on. this is a good thing, you will at least get some protection (though not wearing a seat belt is a bad thing, of course). this is why in the passenger seat you have to MANUALLY DEACTIVATE the air bag if you fit a baby seat.
its dangerous advice because simply not plugging in a seat belt will NOT de-activate the airbag, DO NOT rely on that not to trigger the air bags and decapitate your baby.
similarly when working near any of the airbags including side ones DO NOT take doctor gollums advice and think that because the seat belt is not plugged in you are safe from airbag detonation. you are not.
similarly no objects must be placed in the area in which the airbags inflate, as they could cause injury when the airbags are triggered. DO NOT rely on doctor gollums advice and think that because the seat belt is not plugged in you are safe from airbag detonation. you are not.
having said all that some omegas are fitted with "seat occupancy recognition". this is NOT based on whether the seat belt is plugged in, or whether a dummy buckle is plugged in. it is based on a seat weigth sensor. from the manual
The seat occupancy
recognition system deactivates the
passenger front and side airbags if the
passenger seat is unoccupied or a
Vauxhall child restraint system with
transponders has been fitted to the
passenger seat.
vehicles with seat occupancy
recognition can be identified by the sticker
on the front passenger’s seat.