Where do you work, if you don't mind me asking? This sounds a lot like the interview process for research/academic positions; if you've made it to the interview day, there is really no reason to doubt your technical skills anymore, and the interview becomes more about finding out whether you would find your place and collaborators to work with.
It's for research, specifically at an FFRDC. I don't believe there's any sort of "establish your technical skills" portion. My hiring process was a bit unique because I had already worked as an intern for 3 years, but as I understand it the usual process is 1) hiring manager finds the best resumes, 2) hiring manager does a phone interview with those people, and 3) hiring manager invites a few of the best prospects out.
The real technical skills part is the presentation. If you can give a good, 40 minute talk about what you've been working on, you've already put yourself in a good place.
