When getting the output of postconf -d, there are many items missing from the published list of available parameters. If one assumes that the missing parameters are not needed, that might explain part of it. However, when the missing items contain references to items such as DANE and TLS settings, one might well question if the settings are correct.
Also, there are many included parameters which are not recognized by Postfix. (Were they ever?) The user is left to wonder if they should be there.
How can the user know what is required by Webmin/Virtualmin as opposed to industry standards?
By the way, I referenced the list at http://www.postfix.org/postconf.5.html.