A guess here, I found this comment in my version of C:/Perl/lib/Net/FTP/dataconn ($VERSION=0.11) in the abort function.

# for some reason if we continously open RETR connections and not
  # read a single byte, then abort them after a while the server will
  # close our connection, this prevents the unexpected EOF on the
  # command channel -- GMB
[download]

In this case the code aborts - it does not appear to update the error message.