I have no idea. It doesn’t make any sense to care about this. Virtualmin isn’t explicitly configuring a redirect here, and as far as I know, it isn’t an explicit redirect. It is Apache doing what it normally does in a name-based VirtualHost configuration.
I can’t imagine a situation where you would need to use the IP of the server, and, Apache will show one of your websites when you hit the IP. So, set the default website to be the one you want, if it isn’t already, and move on. You’re obsessing over something that doesn’t make sense. You don’t need to use IP addresses. We live in the future where names can be automatically mapped to IPs via DNS and the web server can determine what site you want based on the hostname in the request header.
Maybe it’s possible to create a VirtaulHost where the ServerName is the IP address but that seems dark and terrible. I think you should stop all this before you go mad.
Also, I don’t think you ever configured a redirect as you think you did. There isn’t anywhere in Virtualmin or Webmin where you can configure “redirect IP to domain” (at least not without writing the redirect rule explicitly), because that’s not a thing people do. There definitely isn’t a button for it (there is a way to set the “default” site, but that’s not a redirect, that’s making the default site the first in the list Apache sees, so that it chooses it when nothing else is a better match because Apache chooses the best-first match for a request).