If you're passing FAANG interviews without prep, you're in a very small minority.

Maybe you're a genius. In any case, your experience is not particularly useful to the rest of us.

Failing behaviorals is also usually a result of poor preparation.

This is very clever reasoning. "Of course I understand how these interviews work; of course I understand what it means to pass them. Hmm? No, I have a lot of trouble passing them. Oh, you don't? Well your experience is irrelevant."

What if — and hear me out on this one — the people passing these interviews consistently understand them better than you do? I know, it's a nigh incomprehensible concept, but if you really struggle with it for a while maybe it will make some sense.

Surely the answer is found in data of how many people do and don't need to prep, not in you being as confident as the other side that you know best based on your personal experience?

But what do I know, I've never even looked at leetcode so maybe I'm missing some trick to extrapolate from anecdote to data accurately.

My experience has been like yours. I don't prep, I don't memorize, and I don't worry about the answers, because they don't matter. I just put my engineering hat on, work my way through the problems, and communicate as I go. Maybe I find a solution right away, and they throw me a twist to take it further; maybe I struggle, and they have to give me a hint; maybe I work at it for a while and explore a couple different approaches, but never actually get there. So what? The process is the point, and I show them how I work. I almost always get an offer.

I think maybe some people are mistaking job interviews for university exams.

Right, you left out the next part from the quote - "(yes, there are people who have done it, they are the minority)". Congrats on being able to consistently pass without prep - I stand by my words that most passing candidates are not in the same boat. I've heard enough comments from folks on the inside about the factor that luck played, and how they would be unlikely to pass again.

Look, I spent a nontrivial amount of time on study. Was it worth it? Yes, because I was able to achieve my goal. Did it have any relevance whatsoever to my actual performance? None. at. all. I would've done the exact same job as prior to the prep. I also know for 100% that I wouldn't have passed without it. That is why I argue about this process - it doesn't convey any real signal about me as an employee, it's all theater.