I'm sure they test those to some extent. I assume it's just a fraction of users affected, so it could be something like a service reading third-party app data

I'm sure they test those to some extent. I assume it's just a fraction of users affected, so it could be something like a service reading third-party app data and crashing due to a bug. The kind of thing that should be caught in code review, because comprehensive testing is next to impossible.