You're taking a saying too literally. People who take on task of writing such library, and develop it to the point it's a language-wide standard, usually know

You're taking a saying too literally. People who take on task of writing such library, and develop it to the point it's a language-wide standard, usually know what they're doing (or learn on the job :) Popularity of such library helps test it thoroughly on many platforms in various conditions, so there's a high chance the bugs will be spotted and fixed.