In my case being handsome and communicative helped me in lot of cases on oral exams. Sometimes i didn't read the whole book, or didn't prepared fully, so i had some holes in my knowledge, but older professors (aseptically grannies) tend to avoid questions on the fields i look insecure about, give an A fast, and then chitchat about my future plans etc. Its not just the handsomeness, if you look secure, have a charisma, make intelligent puns, so to say looks like a "successfully young human being" older profs just dint want to fuck with you. "i would like a grandson just like that" or something similar cross their minds i guess... Maybe the old ladies think of something way more nasty