When ls-names are off, the file's owner displayed from /bin/ls becomes ftpuser, and the file's group, ftpusers. You may also see this occur when the user ID or group ID does not correspond to a name in the /etc/passwd or /etc/group file.
You may find that after adding a user to the system that the ls-name is not displayed. This is because the names are only loaded at periodic times to avoid repeated processing of the passwd and group files. Eventually the change is noticed and the name will be re-loaded.
The a-ls-names controls the setting for anonymous users, while u-ls-names controls the setting for the non-anonymous users.
Examples: