Same trick worked for young me when I started dating...

> I wouldn't be surprised if deciding not to worry about details with unknowable significance and inconsistent response allowed you to relax a bit more in future interviews.

Oh, for sure.

I hadn't interviewed for over a decade, and was super keyed up for the first few this time around. After my attitude changed to more of a "meh, I can take this or leave it" they got a whole lot easier.

I got a recruiter email just today looking for people with my skills and "passion."

Confidence is key and they need to be selling themselves as much or more than you. You don't really need the job. If there is a way to swing disinterested interviewers is another story.