Why is the Use Windows authentication checkbox disabled?

I recently installed HeidiSQL (64 bit) on Windows 10. It is a great program!

I have created an OleDB provider for MySQL using the connector-C from MariaDB. After some drama, I got windows authentication to work in my provider.

This is not a critical problem at all because I can connect in HeidiSQL using a conventional username/password.

I was just wondering why the 'Use Windows authentication' checkbox is disabled in HeidiSQL's connection dialog.

I can confirm that the auth_gssapi_client.dll, required for windows authentication, is present the HeidiSQL plugins folder.

Just curious. Does anyone know?