I think it depends on what the "probability" is meant to indicate. You're correct if it's meant to indicate whether a particular attacker can get through a par

I think it depends on what the "probability" is meant to indicate. You're correct if it's meant to indicate whether a particular attacker can get through a particular hoop. But probabilities could also refer to e.g. the chance that it's possible to get through a particular hoop, period. Or the fraction of some input space which corresponds to an exploitation.