Ask HN: Source for Art and Fear ceramics story

Classic story goes something like this:

A pottery teacher told half his class that their grade will depend on one single piece that they'll produce at the end of the term. He told the other half that their grade will be based on the volume of all the pieces they create. Which half do you think produced better work by the end?

It is used a ship fast, ship often teaching moment, and I like it. However, I can't find any sources of any ceramics teacher who has ever done this.

Anyone have any sources? Feels more like a parable than a real story right now.