“Tell me about a software project you played a significant role in. What did it do, how did it work, who made the tech choices, what was your role in it, what went right, what went wrong, if you were to rebuild it what would you do differently, what did you learn?”
I know it’s really a lot of questions but it’s still just one in a way “talk to me, in a free form back and forth way about software development”.
That said, I do think it's best to have the person relaxed and at their best, so anything to minimize stress or discomfort will show candidates at their best.
Having said that I have open source projects to point to. If that’s not enough for them I’ll take different job.
What if the exercise were something straightforward, simple and given before the interview? And, you had the option of instead discussing a solution of equivalent or greater complexity.
You generally want to cover a range of skills, and technical skills like the ones covered in the article are an important part of that.
If a grad has written no software, or has no capacity to talk software development with you, then the interview is over.