Arm CPU Modeling Engineer interview questions

Applied via staffing agency in UK. It took almost a month for ARM to short list my profile for above position. The interviewer was friendly but spoke very fast and I was applying from outside UK. So it was little difficult for me to understand every word of his. Nonetheless, I answered most of the questions related to RTOS, scheduling, CPU architecture, interrupt handling confidently. Even he indicated that I was quite right about the answers. In the end he asked couple of questions about cache, virtual memory and if I knew about virtualization. Overall the call lasted 45mins. As per the feedback I was rejected because I did not have experience in cache, virtualization. I felt it was unfair since none of these skills were listed under essential/desirable skills in JD