I actually had the opposite at my interview where I currently work. Two-phase interview, first part being credentials, am I a fit for the company environment, how are my people skills, etc. Second part was the technical interview where I showed that I was actually capable of doing the job.
So I showed up to the first interview with a suit and tie, standard business formal that I assume for most interviews. My (now) boss didn't have shoes on. My (now) project lead had a t-shirt on that said "epic fial". I showed up to the second one still (intentionally) slightly overdressed in a polo and khakis. Boss yells from his office as I'm being let in: "He's not wearing a fucking tie again, is he?"
Yeah, I have a pretty great work environment.