They don't. And it's me that has worked in insurance, not John.
There is no perfect system for assessing student performance, and if memory serves statistical normalisation of grades is a routine part of exam marking, to minimise the risk that this year's exam and last year's are radically different standards. It was probably already the case when you and I were doing A levels.
This year's fiasco is horrific, and all the more so for being utterly predictable, and utterly avoidable - the exams were cancelled about 5 months ago, which ought to have been enough time to sort out a robust system.
I was rather surprised that the cancellation happened so quickly. If they hadn't been cancelled there was plenty of time to sort out an alternative way of administering them.