I have no dog in this fight, but his description lines up with my experience. I showed up at Cal in 2001 as a nerdy kid super-jazzed about math. I took Math 1A my first semester, and the lectures started with the professor turning his back to the class and proceeding to write proofs on the board for 90 minutes in indecipherable handwriting with little to no explanation. People would show up to class with pillows, no joke.

I got a middling grade (B+), but the experience was so bad it was the last math class I took. It took me seven years to fully realize my mistake and get back to working in line with my passions.

Anecdata I know, but at least one case where bad Cal math instruction derailed a trajectory.