I have never once filtered someone for lacking confidence. I have never seen someone filtered for lack of confidence by any panel I've been on or any panel I was the hiring manager for. At this point in my career I have interviewed ~1000+ engineers.

I think you're interviewing with the wrong people, or at the wrong places. Way too many people treat interviewing as a way of demonstrating intelligence via computer science trivial pursuit. 5 minutes with Google will demolish 99% of the questions you might ask if all you care about is getting correct code on the board. The interesting part is the process and discussion the code creates, not whether or not they know the secret handshake.