I've created ticket CONNECTORS-804 to cover the documentation being out of date.
work that added the "Override target URL" was done as part of
CONNECTORS-574. Once your page is determined to be a login page, it
allows you to override the target URL of that page to a URL of your
choosing. So, for instance, if it is a form, it overrides the form
action URL; if it is a link, it overrides the link target; etc.