I noticed that the default /etc/hosts file has a comment saying not to alter the localhost.
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1 localhost
It made me wonder what alternatives there were for adding additional hostnames for the loopback IP.
This article on dscl (https://tomafro.net/2009/07/dscl-the-easy-way-to-add-hosts-o...) is one such finding.
If anybody has suggestions about the best way to add hostnames for testing/override purposes, whether that's /etc/hosts or something else, please comment with your favorite.