There are metrics for ASIC quality but without exhaustive tests on every single chip individually (which just isn't worth it) it isn't really possible to implement that - it is much cheaper to just assess a range that chips will work within and set the minimum voltage for that.
No. They are taking the worst case and put it on all the cards which is very incorrect. The exhaustive tests will be run like machine learning by the consumer himself, not in the factory. They will run in the background while the GPU is loaded.