I noticed the same thing more than a year ago:
> Note that NetBSD 6's postconf does not support expansion, so if > backported, the -x must be dropped. https://mail-index.netbsd.org/tech-userlevel/2015/07/27/msg009263.html My mail includes a fix that expands $config_directory, so works with NetBSD-&'s Postfix.
