It was one of the team members, not a manager or lead, so I would have been inclined to overlook it had it not been alongside 3 other "case interviews" that were tricky whiteboard coding/math problems in disguise. I think I spent a grand total of 20 minutes of my 8 hour day discussing my history and relevant experience.
Companies should really adopt shadow interviewing more. Go into an interview and watch someone experienced do it, so you can learn more about how to make interviews pleasant (even for a candidate that doesn't know what they're doing).
I’ve concluded 1:1 in person interviews are insta-fails. With out any witnesses, the bozo interviewing you will just do, say whatever. I’ve had a handful of experiences like the GP and there’s no recourse.