LinkedIn Software Engineer In Machine Learning interview questions

Phone screen then onsite. Phone screen: 1 coding question and 1 question regarding precision/recall. Onsite (6 rounds): 2 coding, 1 product design, 1 ML theory, 1 lunch, 1 behavioral. They asked a lot of questions in ML theory round. Recruiter's feedback: 1. I could not answer "what is '1' in F1 measure?" 2. I just describe superficially. Actually, I started thorough descriptions at the very beginning but the interviewer stopped me. Seemingly, the interviewers are biased toward people from Statistics or a certain country.