Yes, don’t be fooled. Even those handwritten Christmas cards saying hope to see you next year don’t mean anything.
Every year, kids report being admitted to schools where they had GREAT interviews and rejected by schools where they thought they’s be a shoe in because the interview was spectacularly good. Every. Single. Year.
Keep in mind that as of the time of your interview, the AO has not yet read your file. I’m sure the AO generally enjoyed his/her conversation with you. Unfortunately, they can only accept a limited number of students and many who get turned down would fit in and thrive there. They are trying to build a well rounded class though so your chances of getting accepted has a lot to do with what is unique about you and what you will contribute to the class. Not getting accepted does not mean the AO didn’t sincerely enjoy talking with you. Also, FWIW if parents and child believe a certain school is the perfect fit for whatever reason, I would suggest having both parent and child write the AO a thank you note. In my parent note, I expressed the reasons why my husband and I believed the school was a perfect fit for our daughter by referencing aspects of the culture, special programs, the school shared our values etc. My daughter wrote thank you notes to all of her AOs. I only wrote a somewhat lengthy very sincere email to the one school we really wanted. For one daughter I came right out and said if accepted, she would attend. For my other daughter, I fell short of this because she wanted the chance to revisit. I think it is good for the school to know the parent and child are on the same page.
Most interviews would make you feel like that, they’re trying to sell the school along with making an analysis of you as an applicant, I feel.
I feel I had all great interviews, but I could tell there were some better than others. I hope my interview contributed even a little bit towards a positive admission result. 
Ugh. So I posted this question a month ago and was concerned with managing my daughter’s expectations and possible heartache if the news comes back negative on 3/10. When the AD offered to get my daughter in contact with a current student I was hesitant but my daughter thought it was a great idea. She responded that she would love to hear from a current student if it wasn’t too inconvenient. That was a month ago and she hasn’t heard from anyone. Now she’s starting to doubt herself and her chances for admission. This process is going to kill me. Stepping back and trying to just be a supportive parent is harder than it looks. :-S