Code looks clean and readable. For that size, it does not require that much comments (perhaps none at all.) It's not just about good comments, but also good code, and the later is more important than the former.
If we were looking at a more complex/larger piece of code, I would say that comments are needed. But for that (specially the way it was written - well written), I don't think so.
I think it is unfair and vain to put doubt on the applicant given the piece of code submitted by him/her is quite acceptable and did the job.
