It's perfectly reasonable to assume software generally works, because it generally does, and if it didn't we couldn't run modern society on software like we do

It's perfectly reasonable to assume software generally works, because it generally does, and if it didn't we couldn't run modern society on software like we do right now. It's the proper default presumption to make. But the evidence to the contrary could have been something as simple as showing patch notes addressing a bug, or online complaints about that bug, which could have affected the software in a way that gave rise to the circumstances of the lawsuit.