I love these threads. They always show what an absolute dice roll the interview process is. OP rates people taking a best guess at a problem they don't know as a positive character trait, this one rates it as a character flaw.

Google didn't reject the candidate, the interview loop he got rejected him for any of the myriad of knee-jerk split-second decisions made on the candidate's character in an unnatural and stressful environment.

I've been in hundreds of interview loops at $Megacorp. You can stack the deck with preparation, but sometimes you just hit a loop that doesn't click with you.