Superhuman Full Stack Engineer interview questions

I was interviewing for a senior position. Was contacted by a recruiter, a week later was interviewed by a guy. First 30 minutes we were talking about my experience and the company. They are proud by their engineering and sleek product. All in all in was very usual - the guy read the questions from a list and typed my replies. The rest of the interview were "technical" questions about Javascript and web development. There were tricky questions in "you don't know JS" - style. They decided to pass because: "There were Javascript questions that weren't explained well enough .... it seemed like the question wasn't fully understood"