Re: Unknown -passphrase switch in open command.
Your syntax is wrong.
It should be:
See https://winscp.net/eng/docs/commandline#syntax
It should be:
winscp.com /command "open sftp://<username>@<host>.com/ -privatekey=""C:\....ppk"" -passphrase=""<passphrase>"""
See https://winscp.net/eng/docs/commandline#syntax