Oops - I didn't read far enough. 'Mastering Jakarta Struts' goes on to say:
In the normal definition of the Connection class, this method would close the connection to the database and thus render it useless for later processes, but because this Connection object is an instance of a wrapper object, the Connection is returned to the pool for later use, instead of actually being closed.
That certainly answers my question.
Thanks Mr. Goodwill!