agreed. We are not talking here about the chance of not returning from a single sortie, but of not returning.
If the Met man is offered a trip to Berlin and turns it down, his chance of not making it back is zero.
If he goes along, it is say 3% or the chop rate for that trip.
If he is as mad as a hatter, he takes every ride offered throughout the war, and, reductio ad absurdem, if the war went on for ever minus a day, we would not expect him to be casting the runes or consulting the seaweed awaiting the last trumpet call.