As to the questions, being defined or just flowing naturally, it seemed like a mix.
I was asked a lot about my experience writing full feature length projects. This may have been because both of my submissions were shorter submissions, my thinking when I submitted was that I wanted them to see how I handled a full - beginning, middle, end - story in both cases. So that may have been something they specifically wanted to find out about me based on my submissions. I've written 4 features with 2 of them being produced in the low/no budget realm - that seemed to adequately answer the question. For me there was a big emphasis on that, feature experience, what features would I like to write at AFI etc etc etc. So this part may be more based on what your submission materials were.
Some of the questions that seemed possibly more defined were what have I watched recently? And what did I love that I watched recently and what did I hate that I watched recently? Why do I want to be a screenwriter? In my case I'm a "do it all" type so there was a lot of curiosity around this question in light of my production experience and acting experience.
Other than that the rest of the conversation seemed to flow naturally, albeit guided by Anna Thomas.
Oh and they initially brought up my degree. As part of deciding I wanted to go to AFI I spent the last few years getting a B.S. degree in Digital Cinematography from Full Sail (so that when I applied I could qualify for the MFA program at AFI instead of the certificate). So that was brought up early and led into the "So, in light of your background, why a Screenwriter now?"