The responsible thing to do is to have a robust code review culture and cover your code with enough tests that boneheaded mistakes in this vein have a very low

The responsible thing to do is to have a robust code review culture and cover your code with enough tests that boneheaded mistakes in this vein have a very low chance of making it into production. There is no amount of experience that can prevent boneheaded mistakes. If your users' privacy depends on your programmers understanding all the footguns and weird little corner cases in the tools they use, and on implementing that understanding perfectly whenever they write code, you already don't deserve said users' trust. Is it fair to expect a candidate claiming fluency in language X to back that claim up? Sure. But I don't think the general thrust of your comment is very productive.