I would draw the opposite conclusion from that data. The mode difference was 0, and 91% of people were within 1 star of the interviewer. Without knowing what the interviewer's bar is for any particular star level, I don't see how the interviewees could do any better. Rounding to 1-star increments amplifies relatively small changes -- if the interviewer rounds up 3.6 to 4 and you round 3.4 down to 3.
For the purpose of this article, interviewer ratings are considered the absolute truth while interviewee ratings are not, which is obviously not always the case in reality.