In the early days of the variable displacement compressor, some still had clutches. My '06 Volvo is that way, the clutch engages just once, the first time the compressor is needed, and stays on 'till you turn off the car.

The variable compressor is a "first world" thing, probably in other markets they use the simpler old stuff, which is why you would still have a place for the relay.

Given this new info, do you still think you need a kill switch?