I was explicitly told to memorise the principles and the recruiter quizzed me on them during the first screening interview. Good to know that's not the norm I guess, seems like a bizarre thing to do especially for a technical role.
Regarding bar raisers, I don't see why an unrelated and unqualified person from an unrelated team that the candidate isn't interviewing for should have any say, let alone the ability veto their entire application. There's no way to spin that to make it seem like a good idea - at best you're unnecessarily empowering someone who can't properly assess a candidate, and at worst you're saying to the other interviewers that they can't be trusted and need to be supervised. I can understand the need to ensure the quality/integrity of the hiring process, but that doesn't check-out as a motive when the bar raiser isn't typically someone who's qualified to assess the integrity of process.
Also the name itself is a red flag; "bar raising" sounds like it's going to be one of those jobs where just doing your job isn't enough and you're expected to "put in 110%" - which normally translates to unreasonable workloads, unreasonable expectations, and high levels of internal competition. Whether or not that's the case, I can't say but it's the impression that the name gives me.
On the interviewers; the recruiter was slow to respond, disinterested, and rude. The person who I believe was the hiring manager was on his phone during the interview and didn't really engage, and one of the other people involved would cut me off mid-sentence repeatedly. Overall with that + "bar raising" I left with the impression that this would be a toxic environment, and pulled my application (to which the recruiter never responded). FWIW this was all for a role in Sydney, I understand Amazon is very large and experiences will differ between regions.