Earlier quoted context omitted.
It's probably per-team, someone on here mentioned that's how Google works at least. Someone I know did an AWS interview round during business school, and they do this thing called "bar raising" (IIRC) that involves one of the interviewers literally doing something unpleasant to see how you react (e.g. picking their teeth in the camera, cutting you off when you speak). Very odd.
That is not what bar raising is intended to be. There's always a bar raiser in an Amazon interview loop who is not affiliated with the hiring team. They ask the same kinds of questions as the rest of the interviewers in the same way, but they're not influenced by how much the team needs to make the hire, which in theory prevents the team from lowering the bar just to get a warm body in. I'm not saying your friend did…
I'm guessing the way Amazon interview for business roles is somehow different than how they interview for specific team positions. As I understand it, MBA hires aren't filling specific gaps on teams, since the hiring process is so long and involves an internship. There wouldn't be a "team" to lower the bar for, in other words.