FTP Problem with Auto "Use HOST command to select host on the server"

I have the latest WinSCP and have encountered a problem logging into a site hosting multiple FTP sites.
When the option Edit > Advanced... > Environment... FTP > "Use HOST command to select host on the server" is set to "Auto", login fails with the following message:

Authentication failed.
Connection failed.
Valid hostname is expected.

The server is responding with a 530 error because it doesn't know which site I wish to login to.

The work around for this is to set the "User HOST command to select host on the server" option to "On".
Surely the point of the "Auto" option is to detect the "530" response and attempt to login with the host details?

As documented, the Auto currently behaves as Off.
https://winscp.net/eng/docs/ui_login_ftp#host
The 530 response is not specific enough to indicate that HOST command is needed.