Every interviewer wants you to let the guard down and show them the real you. We know the version of you that comes to our interview will be copacetic, genial, nice, friendly, etc. by default. Our biggest task in most of these interviews isn't necessarily ascertaining whether you can develop software -- hopefully that's borne out of some pretty straightforward questioning.

The real task is to figure out what you're really like after the interview facade goes down, and being able to envision you as part of the team.

It's a reason there's so much thought and discussion these days on ways to effectively anonymize people during job searches and interviews, I think. An interviewer / hiring manager needs to be very aware of their own feelings and mindset when making a decision to ensure the "seeing you" part of the decision process is done consciously and purposefully.