The manual page says, "By default, the local port is bound in accordance with the GatewayPorts setting."

I don't see GatewayPorts in any of the config files, so the binary (at least mine) is probably built to have this off by default. Which seems like a sensible setting.

EDIT: It can't hurt to be sure, though. Especially if you're running ssh commands on different computers or writing a script that runs ssh.