If they flub half of the time and go on seven such interviews, they have over a 99% chance to pass at least one of them.

And that’s for someone with only a 50/50 success rate at summing an array of integers. Do you want to hire someone for a software role who is an underdog to be able to sum an array of ints?

Interviews are learning experiences, you get better at it the more often you do them. My first comment in this thread was that this guy was just a learning experience for these students. Summing integers is easy, understanding someone’s rushed description of what they want done along with rushing to code or write a solution on a whiteboard is the hard part.