Canon Medical Informatics Software Developer interview questions

I applied for a software developer position and several months later I received an invitation to do an interview. After a standard interview with a hr person, there was a technical phone screen on C++. The technical interview was being done by the VP of engineering, which seemed a bit awkward and left somewhat of a small company impression to me. The phone screen itself consisted of pretty standard C++ questions on topics like operator overloading and polymorphism which the interviewer obviously read from a list. The interviewer seemed happy with textbook definitions of C++ concepts but when I departed from the standard textbook definition and explained a concept with an example, he hesitated and did not seem to understand the answer. I guess he was just reading questions with their answers from a list and if my response matched the answer he had on his list, he was happy. Otherwise, he just didn't know. I would rate the interview being of average difficulty. A few days later I received a reply that I had not passed the interview. The same week I had a much more difficult C++ interview at another company which I did pass. So I am not sure whether it were the interviewer's C++ skills or my C++ skills that caused me not to pass.