In addition to the people overtly saying this makes you a no-hire, it's almost impossible not to use this even if you try. Someone smooth and mistake-less will make a better impression on you, and like with most fallacies, you're left flying blind on how much to adjust your expectations to counteract it.

I think those people are the vocal minority. In my experience most interviewers will go out of your way to get you to feel comfortable and relax during the interview process.