He specifically calls out the use of the material in a place it wouldn't be seen as something that the carpenter making beautiful cabinets wouldn't do, but that's actually something they absolutely do. He's trying to argue some other point by way of this analogy, but his analogy is wrong because he doesn't know anything about it. It would be like if I was trying to argue my point by way of car analogy but the example I chose was to say that car enthusiasts insist on genuine OEM parts, I'm only exposing myself as somebody who doesn't understand car people.