Dbt is aimed at addressing the skills you need to help cope with overwhelming emotions. It also is supposed to help move away from si as a coping skill. I know the interview sounds (and can be) intimidating, it's to help the t get to know you a bit better. They would want to know about the si because dbt would directly address it. While you are not processing things that come up, you do process events and scenerios to a degree. It's interactive. They do expect you to talk about how you handle things and your thought processes.
I've had different types of interviews for different dbt groups, so your best bet would be to call the t and ask what's involved. Even though it's a skill based intervention, they tailor it to your particular issues so you can get the most personal benefit.
In the groups I attended, we were expected to give an overview of our struggles, but not expected to go into detail. I would talk about having am abuse history, and struggling with self harm, but wouldn't be expected to divulge details to the group...
I'm sure this doesn't really help. Sorry... hope someone else chimes in. (Keep in mind I also am very triggered by dbt because of how it reminds me of my childhood. I'm definitely biased against it for myself, though it has value as an intervention).