Employers don't actually (in most cases) have a very good grasp of what qualities they select for. It's function of the engineers doing the interviews and the engineering culture, and most companies are not aware how much this differs between companies. We model what each company looks for by sending them candidates with specific attributes and reading their feedback (we get honest feedback from companies after interviews, which is pretty rare). We're then able to see how feedback for the same candidate differs between companies.