Hi Eli. I don’t disagree with you, nor would I say the interview should not cover your portfolio. I think the point I was making refers to when the majority of the interview is nothing but an evaluation of your portfolio. And, that may not necessarily be a red flag as long as you get appropriate engagement. However, I have been through a lot of interviews where I was 5–10 minutes into my presentation and knew I had lost my audience because they didn’t understand the complexities of the project.
You are also right concerning how a portfolio review can be an opportunity to find out more about a designer’s thinking skills and motivation. But, the interview has to be conducted appropriately. Jared Spool has a very good article briefly covering this.