If I understand correctly, this module is meant to automatically trust the reverse proxy the request is coming from.
It is not very well documented but it is possible to do this:
$settings['reverse_proxy_addresses'] = ['REMOTE_ADDR'];
Request::setTrustedProxies() will then automatically add the address from $_SERVER['REMOTE_ADDR'] as a trusted proxy.
If you also want to trusted every private address, I think you can do something like this:
$settings['reverse_proxy_addresses'] = ['REMOTE_ADDR', 'PRIVATE_SUBNETS'];
Does the module do anything additional that can't be achieved with these settings (apart from removing the trusted host pattern requirement) ?
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I mean, no, there's not a significant difference, but this allows you to do so without any specific changes to settings.php and also does some sanity-checking on the validity of the configuration. And, it demotes the warning message that is otherwise distracting.
But yeah, you can do whatever you like with same effect. I think this is pretty well explained in the project readme.