I tried your command with an empty local target directory. I wound up with a directory tree containing no files. Here's the FTP commands and responses from one (of about 70) connections. There are no GETs; i.e., the SYNC command didn't ask for files. And note, Rex, the CWD command with no args generates a syntax error response.
[02] Tue 22May12 22:36:26 - (000306) ANONYMOUS logged in, password: JPUser@
[21] Tue 22May12 22:36:26 - (000306) 230 User logged in, proceed.
[20] Tue 22May12 22:36:27 - (000306) PWD
[21] Tue 22May12 22:36:27 - (000306) 257 "/" is current directory.
[20] Tue 22May12 22:36:27 - (000306) CWD /RoadRunner/
[21] Tue 22May12 22:36:27 - (000306) 250 Directory changed to /RoadRunner
[20] Tue 22May12 22:36:27 - (000306) CWD
[21] Tue 22May12 22:36:27 - (000306) 501 Syntax error in parameters or arguments.
[20] Tue 22May12 22:36:27 - (000306) PORT 74,71,17,28,242,150
[21] Tue 22May12 22:36:27 - (000306) 200 PORT command successful.
[20] Tue 22May12 22:36:27 - (000306) LIST /RoadRunner
[21] Tue 22May12 22:36:27 - (000306) 150 Opening ASCII mode data connection for /bin/ls.
[21] Tue 22May12 22:36:27 - (000306) 226 Transfer complete. 185 bytes transferred. 0.18 KB/sec.
[20] Tue 22May12 22:36:27 - (000306) QUIT
[21] Tue 22May12 22:36:27 - (000306) 221 Goodbye, closing session.