It's more technical than that. There are three flaws of listening, that are similar to the illustration of a cup (or bowl).

1. A dirty bowl (a listener perverts what he hears),
2. A cracked bowl (the listener doesn't retain anything he hears), and
3. An upside down bowl (the listener is not open to anything new).

The Zen story offers a fourth possible flaw of listening, a full bowl (the listener is full of busy thoughts).