Well, there's layers on layers of subjective here, starting with the recruiter's tale and your interpretation of it. But I don't see any fault in the logic that candidates who are "confident" to the point of being full of themselves get passed over, either because they're overrating themselves or they irritate the interviewer. Some confidence is good. Trying to appear Superior with a capital S or invincible isn't. That you believe you have the chops and will do your best in the position is probably the right general attitude.

Maybe you didn't pick up cues from the interviewer. Or maybe you had great answers but it wasn't what the interviewer asked or was looking for.

It's anecdotal; I wouldn't put much stock in it. As Therblig noted, I can see cocky and arrogant people being passed over. I can also see incompetent people thinking they did great. It is a mistake for anyone to walk out of an interview thinking they got the job.

go read some of the HR / Interview stories on reddit sometime.