Here's another example of a similar but slightly different failure mode of the live defense: The department where I got my degree had a practice around PhD defe

Here's another example of a similar but slightly different failure mode of the live defense: The department where I got my degree had a practice around PhD defense where there would be a prof each representing the four research pillars + the dean. It was well known that certain professors disliked each other enough that they would snipe each other's candidates. You'd just hope not to work for one whose enemies got picked for the panel. If you were a superstar, you'd pass, but if you were an okay candidate or someone strong but with stage fright, you be could toast even if you did good research. The defense was only briefly about the actual thesis, then switched over to whatever research interest the committee members had, and they'd drill into their pet subjects. This was in physics, hardly politics forward normally, and at a very well respected university.