I have deep knowledge of the underlying technologies, mostly deep knowledge of the languages. But my experience is that most interviewers do not care about this. They want to hear about your last project using their laundry list of libraries. Everyone wants me to assure them that I am a "React expert" or that I have "used AWS" and no one cares about the papers I've read recently or the first-principles, ground-up projects I've done. The only time anything approaching specialized knowledge comes up is when people ask trivia questions.