A lot of you have a lot of faith in people reviewing PRs. I know a few Sr. developers, that if shit was too busy, would skim it and say 'fuck it, it will be QAs problem. If you put this in the correct sub-system in file that would only be executed once a month, for example a maintenance class, It would be really hard to notice something is wrong if it didn't cause issues seen immediately. Maybe this is the story of an intern that added something that also fucked up boolean comparisons in a subsystem used once a month. Where there is a 2 week lag between the execution and operations noticing something wrong.