I was an engineering manager an for decades and I did first technical phone screening of a very large number of candidates. I couldn't really assess someone's design and programming skills. So I would pick a particular area they were promoting and go as deep as I could on it, both on the technology and their project experience using it. I weeded out lots of candidates, saving my engineers' interview time for more suitable candidates. And my teams were good at giving me feedback when I let someone unqualified e slip through...