my first 1:1 with a new manager felt like an interview all over again and I wasn't ready for that

First 1:1 with a brand new manager and she came in with a list of questions about my background I hadn't prepped for at all, felt like round two of the interview loop. Answered fine but was thrown by how much it caught me off guard given I already had the job. Wish someone had told me the first 1:1 is basically an interview you didn't know you signed up for.