I don't know. I never graduated to waiter, but I worked as a busboy a few times. I have much sympathy for wait staff. My recollection is that the waitresses were always decent to me. Still I don't buy, "I suspect it’s easier to teach a waitress to be a writer than an intellectual to be a waiter." One of my other low-paying jobs was as a copy editor, and I have seen how commonly schools have failed to teach PhDs to be…
Everyone learns to write in school. A waiting job most can pick up but not all. I couldn't get past serving training. Carrying four plates and keeping them straight takes without spilling is for others.
This is like saying everyone learns math in school. It's technically correct, but only if you ignore the vast difference in skill between the average person and (e.g.) an accomplished novelist.