I can't find the original article that discussed the confirmation bias effect, but this one is close: https://www.plum.io/blog/the-issue-with-the-interview-confir...
I'm familiar with that feeling though. I've had several interviews where I really (subjectively) liked the candidate, and really wanted them to succeed - but having a prepared interview plan ended up doing its job and helped determine that the candidate was not a good match for the role.